Elizabethan London

Elizabethan London
Tyburn was an infamous execution spot west of London, used since medieval times. The Tyburn "tree" - a unique, multi-person gallows - erected in 1571 became a popular public spectacle, drawing crowds of thousands.Tyburn Tree blog is less blood-thirsty but hopefully topical, interesting and informative, if slightly bent to my personal topics of interest - books, writing, history, technology, with a smattering of politics and dash of pop culture, science and the downright strange. So "take a ride to Tyburn" and see what happens...

Sunday, December 30, 2012

Vieux Montreal

We were recently in Montreal for a Bantam hockey tournament (before their record dump of snow).

If you have ever had the opportunity to roam Montreal, I highly recommend making sure you tour through the Vieux Montreal area, in particular la Basilique Notre-Dame is well worth a look.

Pics are below, along with a couple shots of the boys hockey action.  Not a great tournament result for the team, but much fun had by all!
Place d' Armes, Vieux Montreal

Basilique Notre-Dame, interior
Rue Saint Sulpice

Basilique Notre-Dame, interior
Rue de la Capitaile
He shoots....and is robbed!

More action at the net

Rue Saint Paul, Vieux Montreal

Rue Saint Paul, Vieux Montreal
Restaurant des Gouverneres

Vieux Montreal

Basilique Notre-Dame at night

Tuesday, December 18, 2012

We are Anonymous

If you want to gain an understanding of Internet and hacker culture, however cursory, the excellent book We Are Anonymous:  Inside the Hacker World of LulzSec, Anonymous, and the Global Cyber Insurgency  by Parmy Olsen is a good entry point.

The book traces and outlines the evolution and growth of the loose "hive mind/hacker collective" that eventually morphs into the online hacking group Anonymous (typified by the stylized, blank faced Guy Fawkes masks from the film V for Vendetta now commonly seen at protests).

Anonymous is the amphorous, changable and often desultory collection of online hackers, script-kiddies, black-hat virus makers and anarchists that have aggregated into one of the more unique and potentially dangerous expressions of online culture. Olson traces the key elements that drove the development and growth of Anonymous, keying in on its more spectacular denial of service attacks and other hacking activities (including Anonymous's role in the Arab Spring) that have brought down web targets as diverse as CBS and the CIA.  The author takes a detailed look at a core group of hackers, paralleling their lives and the evolution of Anonymous from a loose affiliation of 4Chan message board lurkers and hackers into a more political, radical and anarchic agency.  The movement started from the subversive (and at times vicious) "trolling for the lulz" approach that morphed into Anonymous more by accident then design when it slammed into an online war with Scientology.

We are Anonymous. We are Legion. We do not forgive. We do not forget. Expect us.

Olsen outlines the rise of Anonymous from minor Internet irritant to the bane of Internet security experts everywhere and how the FBI and the authorities in the US and the UK eventually traced back, turned and broke at least a key part of the most significant organized hacking organization (if you can call it that) in the world.

The book is timely, fascinating, somewhat disturbing look at hacker subculture, the darker corners of the Internet and the rise of a new type of collective activist capability that has the capacity to impact commerce, politics and social networks around the world.

It warrants a careful look.

Tuesday, December 11, 2012

In The Plex

"In the Plex" is Steven Levy's a highly engrossing and well-written account of the the rise of Google from a garage start-up to a $30-billion colossus.

The book outlines Google from its initial conceptualization by Larry Page and Sergey Brin, examining the rise of its search capability, the advent of the advertising monster that became AdWords and AdSense (still accounting for the vast majority of Google's revenues), and the sometimes painful growth of the company from nimble start-up to Internet dominatrix.

Of particular interest is the gradual development of Google's market direction and management approaches, specifically in fostering innovation and new business opportunities. The author cites both hits and misses, delving into how Google works, thinks and acts.  Levy examines the many challenges the company has faced with issues such as privacy concerns, copyright issues, the seeesaw efforts in the China market, and the failure to catch the rising tide of the social media market.  The book looks at the evolution of both management and corporate culture including Google's reticence for revealing much information about itself and its the famous 'Don't be evil' mantra.

Google's well-known 20% rule - whereby employees can spend up to 20% of their time working on other projects - is mentioned but is one area of the book that seems sadly under-examined in the book as is very much insight into Google's innovation approaches, beyond the interests of the founders.

Of note to anyone in management is Google's application of OKRs - Objectives and Key Results approach (something devised by Andy Grove from Intel) in planning and setting business objectives and direction across the organization.  The OKR approach provided Google with a fundamental and rigorous objective planning system that was scalable across the rapidly growing organization, helping the new company in ensuring strong objective planning and a cohesive direction.

Well-written and in-depth, In the Plex is well worth your time.

Fenced Decks = Dog Jail

Thursday, November 15, 2012

Going Medieval on The Walking Dead!

Season 3 of AMC's The Walking Dead seems to have amped up from last year, with the intrepid (and dwindling) group of survivors now whittling down dozens of zombies per episode.  I guess the long spell of sitting on Hershal's farm eating carbs last season helped them rest up, but I've still noticed a rather proliferate use of scarce ammunition, which doesn't seem like the optimal way to deal with a zombie threat.

Eventually the bullets run out and you will be forced to tier back to a more traditional methodology for eliminating the walker menace:  hand-held, muscle-driven weaponry.  While the tried and true use of gardening tools and heavy hunting knives seems to be popular on the show, the reality is that using a hoe to brain a zombie might not be the most efficient tool.

When it comes to taking down a zombie with hand-held weapons, the Walking Dead crew might want to peruse some traditional medieval weaponry.

Zombies require a brain shot to permanently grant them quiescence and eliminate the menace.  The human skull is designed to protect and shield the brain and can be a difficult target.  Strikes can deflect quite easily, sliding off to one side or the other, leaving you off-balance and vulnerable to a quick zombie chomp.  Measurements from skull impact tests and force studies have concluded that the human skull can fracture from as little as 16 lbs of force (71 Newtons for you science types) but it is very dependent on how and where that force is applied.

For ideal zombie slotting, you want a hand-held weapon that allows you to strike quickly, with minimal muscle force, maximum leverage, and lots of kinetic energy and precision for the impact.  Ideally, the weapon should have enough reach to keep the slavering monster at an appreciable distance.   The minimal muscle force is a necessity as you probably have a fair number of the undead lined up hungering for your brains.  You don't want to expend any more energy killing them than you have to.

Medieval weaponry, designed for use against armored opponents has strong potential for efficient zombie slaughter, after all, it worked really well on the French at Crecy and Azincourt.

Starting with ranged weaponry, everyone's favorite redneck ninja Darryl Dixon is already well-equipped with a compound hunting crossbow.  Crossbows were powerful weapons, with a longer range and more kinetic energy then longbows but were often slow to reload as you needed to crank or lever them back to shoot again.  A longbow in trained hands was just as accurate, almost as powerful and could be shot at a much faster rate.  The downside to the longbow was that to become effective with one required years of training from a very young age.  A crossbowman could be trained in a week.   Longbow-men in England actually had massively overdeveloped shoulder and arm muscles (evidence of which has been noted in a number of bone studies) from shooting the massive weapons with their draw weights of 100-120 lbs.  Consequently the longbow, though probably better for fast accurate shooting, wouldn't be a practicable weapon for zombie fighting.  The crossbow, with its accuracy and ease of use, would be very applicable but the slow reload might be problematic for personal, in-close zombie fights.

So what's your best in-close, effective zombie-killing tool? 

The traditional medieval weapon that Hollywood tends towards when exploring martial chaos with armored knights is the long sword and broadswords.  I'm not going to go into detail on the wide variety and metamorphosis of long swords (also known as the great sword) across the Medieval period (this site is terrific if you are interested) but I am going to note that swords were often overrated as the melee weapon of choice.  Long swords were heavy and sometimes unwieldy, especially when you started getting into the William Wallace-style claymores.  In untrained hands you were likely to tire quickly and probably accidentally clip Carl, who just can't stay out of trouble. 

As a zombie-killing device, the long-sword has the goods to deliver an effective strike.  The television show Deadliest Warrior tested a Viking long sword against a skull target encased in ballistics gel, to try to assess the type of damage.  The sword test saw the skull almost bisected, prevented from being sliced in half only because of the steel mounting rod the target was fixed to.  The sword actually chipped the steel support rod, so the force involved in being on the receiving end of a strike is considerable and any zombie hanging around the arc of that strike would soon be an ex-zombie. 

First-hand evidence on the show is provided by the season 3 character Michonne, who's dai-katana serves her as a very effective zombie-elimination tool however it is fairly evident that she has significant training.  Japanese katanas are designed primarily as edge weapons, with a focus on cutting.  As a tool for lopping off zombie heads, it is first rate.  The long sword could certainly effectively take out zombies, but would it be the most efficient tool for the job?  There are a lot of zombies.... and heavy, two handed swords can be tiring.

One-handed swords were probably a better option, which opens up the question of what are you using in the other hand?  Often it was a shield or a buckler.  T-Dog leveraged a shield very effectively in helping clear the prison, which brings to mind that the use of a team-based protective shield wall approach might be very effective against small groups of zombies.  Against large groups, the technique would probably be less useful as you would certainly have zombies coming up the flanks and turning the corner on your shield wall just because of sheer numbers.  At which point, you would be lunch for walkers.  But I digress...I think we will save defensive strategies and armor for another time.

One-handed swords are lighter but typically also shorter, which impacts your reach.  Often they are better designed for quick, accurate attacks, culminating the rise of the rapier-style blades when you move into the Renaissance period.  Rapiers would be good, accurate for attacks in through the eye sockets but are designed for killing with the point, not for slicing and dicing.  They probably lack the weight and heft to be effective skull busters like the long-sword   In addition they, like the katana, require a significant amount of practice and training to be used effectively.

The overall conclusion around swords is that while they certainly provide effective zombie killing, they might require a strength and skill level to effectively wield and will probably not be the most energy efficient solutions for when you have undead lined up around the block.  In short, around about zombie number three, you will be feeling the burn...

Daggers, poniards, misericordes, rondels and other hand-held short bladed weapons are another option but you need to be in-close, within biting distance, which makes them problematic.  Designed to be thrust into gaps in armor, through visor eye slits to deliver a killing blow (or occasional merciful deliverance from other wounds) to a fallen knight, these weapons were very lethal.  The only sure route into the zombie's brain however would be via the eye sockets or the mouth.  While a precise blow with these stabbing weapons might be able to penetrate the skull, the chances are high that most attacks would be deflected.  With a zombie, impervious to pain, uninterested in anything other than its appetite, a glancing blow might allow for a fatal counter-bite.  These type of weapons are probably only a last resort alternative for effective zombie fighting.

Moving onward there is the all-purpose axe.  Medieval era battle axes were generally more tapered in the blade and lighter than the typical general purpose axe used around the home, with a crescent-shaped head rather than the familiar wedge.  They varied widely in size and blade type, including two handed variants of all sizes and shapes. 

Of particular note was the poleaxe and the halberd, which were long-handled variants of the war axes (or axe-bladed variations of spears, if you want to take it from the other direction).  With a broad blade on one side and an armor penetrating pick on the other, halberds and poleaxes were deadly killing tools.  Throw in a spike on the tip and they served as effective and deadly combat weapons.  For zombies, the typical war axe would be more than effective and the highest efficiency and lethality would probably be from the halberd or poleaxe format, giving you reach, leverage and the capability to deliver a fatal blow with relative ease, and efficiently leveraging the physics of the weapon in your strike.  You have the option of the axe blade, the spike or the pick, depending on your mood and preference.  As an added bonus the spike on the tip could be used to hold a zombie at bay while your fellow survivor popped the undead in the brain with the pick side, assuming your fellow survivor wasn't Lori who, true to form, was probably off looking for Carl.  The hooked end of the axe blade could also be used to catch at a knight or man-at-arms, and pull him off balance, leaving them open for a second attack.  There was often a spike on the base as well, to be used on fallen foes.

What medieval themed zombie-killing arsenal would be complete without that old standby the mace?  Maces are hard-core bludgeoning weapons, designed to stun, crush and impact through armor.  Probably the weapon of choice for Merle. 

Flanged maces in particular were effective at penetrating even the strongest armor with the protruding flanges denting the metal on impact.  Against an unarmored zombie skull, the flanged mace would be routinely lethal. 

Ideally the best possible position for using the mace would be on horseback, allowing the weight of the weapon to do the work.  Typically horsemen would ride past the enemy and swing the mace back for the impact on their opponent, moving onto the next target without having the horse break stride or slow, which could be fatal in a melee. Whether a horse would proceed against a horde of ravenous zombies is questionable, but one can see possibly riding past in the back of an open pickup and swinging away quite effectively.

Another bludgeoning weapon with a brutal elegance was the war hammer.  These long-handled hammers ranged from halberd-sized (for use on mounted targets) to hand-held, mace-sized weapons.  Usually a hammer was paired with a spike, useful for penetrating armor or hooking foes and their reins.   Designed as bludgeoning impact weapons, war hammers were usually effective at stunning armored knights, even through plate armor.  Against unarmored zombies, the hammer would be deadly as it permitted a massive amount of force to be directed against a zombie's head with a minimal effort, as anyone who becomes practiced at driving a nail can testify.

The last items to discuss are the pike, lances and other types of spears.  Spears are tremendously versatile and dangerous weapons and would be effective with zombies on one-on-one where you could target the zombie's head.  The issue, I think, with them and with pikes, is that a horde of zombies, unlike cavalry, would probably not stop or split when faced with a wall of pikes.  Rather they would end up spitting themselves on the spear and continue moving forward.  I suspect you would end up with a zombie on a stick, which is better than one in your face but begs the question of what next?  Ideally your pikes or spears would have some type of crossbar to prevent them from moving forward all the way to the wielder but aside from an impediment to their movement, a wall of pikes might not provide much advantage.

Other medieval weaponry that might be helpful in a post-apocalyptic, zombie-infested hellhole would include most of the many variations of the above, in all their myriad details.  Mauls, flails, quarter-staffs  picks, and morning stars (these give me nightmares just thinking about swinging one.  You just know that somebody would accidentally spike Rick and end up on the receiving end of the harshest glare in television).

In summary, a good weapon layout for the Walking Dead survivors would probably include a nice mix of "mid-range" handheld weapons and good close-in finishing tools.  My suggestion would be a team of four wielding halberds or poleaxes to engage the zombies at a good distance, and the others armed with flanged maces and hammers for in-close zombie splattering.  Oh, and rondels or poniards for everyone, for that just-in-case gory close-up moment that all the Walking Dead fan base like to see.

Although I have to say, I would pay cold hard cash to see Rick going to town on a horde of walkers with a long-sword....

Monday, November 5, 2012

City of Fortune

City of Fortune by Roger Crowley is a vivid, engrossing historical account of the rise (and eventual fall) of the the city of Venice.  Crowley traces the establishment of Venice as a small trade port and pulls together the fine threads of profit, technology, commercialism, power and hubris that allowed Venice to build an empire, without any natural resources to draw upon but themselves.

"The sea was at once their protection, their opportunity, and their fate; secure in their shallow lagoon with its deceptive channels and treacherous mudflats that no invader could penetrate, shielded if not insulated from the surge of the Adriatic, they wrapped the sea around them like a cloak."

At the height of its power, the Venetians sat at the epicentre, controlling the crossroads of the spice trade between the Christian west, and the markets of Islam, the Mongol, China and India.  From Asia and the Middle East,  to the European markets of France, Italy and Germany - Venice was the linchpin.  This then was Venice's famous "stato da mar", the dominion of the sea, an empire born of trade, inculcated on profit and ruled by commerce over all.

Well-written, concise and filled with deftly drawn historical figures  and incidents, Crowley examines the Venetian arc of history from their "hijacking" of the Fourth Crusade, the fracturing (at their hands more than anyone) of the Byzantine Empire, into their long commercial feud/war with Pisa and Genoa, and their abrupt decline in the face of Ottoman expansion and Portuguese technology.

City of Fortune is a brisk, epic and superlative account and well worth a look.

Tuesday, October 16, 2012

Wonders in a Box...

Google turned 14 years old the other week.  It is now a problematic teenager insisting on staying out late and asserting their independence...oh wait, that's my kid.

I wanted to share a few Google things that are to me, frankly, pretty astonishing, considering that none of them existed in anything other than someone's imagination until recently.  These are technologies that make me genuinely feel as though I am living in the future (still waiting for rocket boots).

Google Earth - Google Earth was purportedly conceptualized out of sci-fi writer Neal Stephenson's novel Snow Crash, published in 1992 (and a fantastic read, if you are so inclined).  He posited a pan-optic  satellite-based, real-time software that allowed the viewer to zoom in and track in real-time to any specific geographic location.  The interface was a 3D, zoom-able model of the Earth, that the user could manipulate at will.

Sound familiar?

If you've ever had the opportunity to mess around with Google Earth, you are probably familiar with the ability to zoom in on specific locations, pivot, re-position etc.  If you have the 3D modelling enabled, it will map land-forms and altitude, canyons, mountains and oceans.  And cities. 

You can zoom about a virtual New York or Venice, populated with hundreds of 3D rendered models, often developed by independent designers.  For students and wanna-be travelers  it is a tremendous planning tool for tracking hotel locations, travel routes and generally getting an idea of where you are in relation to everything else.   And the ability to virtually visit almost any historical and building of note is terrific for any student of history.

As an added bonus You can take control of a basic flight simulator and fly the Grand Canyon or any other location that you've thought an interesting spot to visit.  The 3D terrain is fairly decent, probably not up to Microsoft Flight Simulator standards but considering you aren't paying, it's very neat.

 As a learning tool for anyone who's ever unfolded a map and asked what lay in the blank spots, Google Earth is phenomenal!

Google Doodles - Everyone is familiar with Google Doodles but did you know that Google does specialized Doodles for countries, celebrations, special events cultures, artists, cultural and historical figures of note around the world that most people in North America never see.  Click on through and have a look, it is highly educational.

Google Art Project - Google Art Project is, in essence, a variation of Streetview for museums.  It is a collaborative project spanning more than 40 countries and 151 partners that brings Google's technological know-how into the world's best museums.  With its partners, Google has captured more than 30,000 works of art from around the world and brought them into reach for anyone with access to a computer.

The resolution of some of the images is extreme.  On selected works, you can literally zoom down to view the brushstrokes.  Here's a close up of Hans Holbien's portrait of Sir Thomas More ("A Man for All Seasons", currently hanging in New York's Frick Museum.

Google Streetview - The name says it all but Streetview, a spin-off from Google Maps, has in recent months, gone "off-road", adding pedestrian walks, hikes, new locations and some extreme locales including Antarctica and the Great Barrier Reef, the Amazon, and Google's WorldWonder's Project, which can virtually take you through such locations as Pompeii, Yellowstone, and the Palace of Versailles.

I'm not going to go into the myriad online tools such as Google Translate, Google Docs, or Google Books, suffice to say that Google's mission of putting information within reach seems to be proceeding at a exceptional pace.

So why does it matter?  I think, and its only my opinion, that Google's efforts to put the world's cultural heritage, people, cities and information in a reachable format readily available for public access, is a tool and a project that captures the scale and immense possibility in the world.  It reminds me of all the potential you sense when you walk into a library - endless stacks of books, knowledge and thought on every subject you care to know, content, stories and voices that stretch back across time and space.

Google puts that into my living room.  And I appreciate that effort.

Thursday, August 23, 2012

“It was a dark and stormy night...

It is time again for reams of deathless prose to fall trippingly and winningly (agitatingly even...) onto the page. It is time to read, nay, to declaim with unadulterated joy, the best and most articulate expression of literature that the world, dare I say it, has ever beheld.

In short, the results for the 2012 Bulwer Lytton Competition are in.

Edward George Bulwer-Lytton was the author of Paul Clifford (1830), a book widely remembered and oft-cited for it's florid opening passage:

“It was a dark and stormy night; the rain fell in torrents — except at occasional intervals, when it was checked by a violent gust of wind which swept up the streets (for it is in London that our scene lies), rattling along the housetops, and fiercely agitating the scanty flame of the lamps that struggled against the darkness.”

To honour writers of purple prose everywhere, San Jose University has sponsored the Bulwer-Lytton Fiction Contest since 1982. Thousands of entries are submitted each year, the best of which are selected as finalists and winners for a variety of categories. Earning a nod from the Bulwer-Lytton judges requires a substantial dive into a deep, deep well of sublime, ear-bleeding prose...

Here is the 2012 Grand Prize Winner:

"As he told her that he loved her she gazed into his eyes, wondering, as she noted the infestation of eyelash mites, the tiny deodicids burrowing into his follicles to eat the greasy sebum therein, each female laying up to 25 eggs in a single follicle, causing inflammation, whether the eyes are truly the windows of the soul; and, if so, his soul needed regrouting." - Cathy Bryant, Manchester, England

You can find the many category winners and finalists listed on the Bulwer-Lytton site, it is well worth a look.

My personal favorite - the Crime Fiction winner:

"She slinked through my door wearing a dress that looked like it had been painted on … not with good paint, like Behr or Sherwin-Williams, but with that watered-down stuff that bubbles up right away if you don’t prime the surface before you slap it on, and – just like that cheap paint – the dress needed two more coats to cover her." - Sue Fondrie, Appleton, WI

and the Dishonorable Mention winner (I just can't resist):

"Inspector Murphy stood up when he saw me, then looked down at the lifeless body, crumpled like a forlorn Snicker’s candy wrapper, and after a knowing glance at Detective Wilson pointed to the darkening crimson pool spreading from the stiff’s shattered noggin, and said, “You settle it, Gibson; does that puddle look more like a duck or a cow?” - Carl Stich, Mariemont, Ohio


Wednesday, August 15, 2012

"Slow beats the time-worn heart of Mars..."

If the Olympic excitement has been distracting you, you might want to take note of this spectacular and astounding moment in history - the amazing success of the Curiosity Rover. 

Curiosity is part of NASA's Mars Science Laboratory, a long term series of robotic exploration mission of the red planet.  Curiosity itself is a large mobile laboratory with a payload ten times that carried by previous rovers.  Designed to roam the surface of Mars for at least a full Martian year (687 days), Curiosity is equipped with 17 cameras, a laser spectrometer and sample collectors (among other testing equipment) and is designed to test the Martian soil for potential signs of microbic life.

Curiosity successfully landed last week utilizing a spectacular and terrifying deployment system that combined reentry, parachute deployment and then a final descent via a tethered "sky-crane", a new and innovative landing deployment that had never been attempted before.

Essentially JPL and NASA have landed a rover the size of  mini-Cooper on a planet more than 85 million kilometres away.
Curiosity is currently situated in Gale Crater, a massive 154 km wide crater estimated to have been created 3.5 billion years ago.  The exposed terrain of the crater will allow Curiosity a full view of the range of Martian geology, opening a window into the planet history.  The image to the right (courtesy of NASA), shows Curiosity on the surface of Gale Crater.

For a look at the surface, where Curiosity is currently, I highly recommend clicking on the link for a look at the incredible and immersive panorama that Andrew Boderov stitched together at 360 Cities blog.

Monday, August 6, 2012


Several months back I used Lulu.com to pull together some reader copies of The Jesuit Letter that I could distribute to people and get feedback on the book.

Aside from discovering that no matter how much editing I do, I still manage to find additional typos right after having 10 copies printed....I found myself noticing and attending more carefully to the role of book covers.  The cover I pulled together for The Jesuit Letter was literally just that - pulled together from a couple of off-hand images I had and dropped onto the Lulu template...but this was a for a set of personal reader copies, not for sale or appeal to a wider audience, so I spent very little time considering what to incorporate.  Not being a designer and using a very limited Lulu template, the cover is alright for the use for which it was intended.

But it certainly doesn't do the job it should.

The saying "you can't judge a book by its cover" might be nominally true but I suspect much of the time you can and do judge a book by its cover.  A powerful, interesting or evocative cover can catch the eye and set the tone for the book.  It is, I suspect, an essential component in determining if someone browsing in a bookstore, library, or online, decides that this particular volume merits a closer look.

Certain book covers tend to stick in the mind and help build a compelling and intriguing picture of the book and the story for the reader.  So what works in a good cover? 

It is fundamentally subjective to the reader but there are a number of key elements that are oft cited on design sites.  The basic rules of cover design seem to boil down to the following:

Clarity - A cover should reflect the identifying points of the genre - for example, a reader should be able to easily distinguish between a western vs. a romance or a horror novel (although there may be overlap if the story has elements from multiple genres or crosses genres).  Recognizable identifying points provide context for the reader and help them distinguish the type of books that they are looking for.  They will recognize and cue on the key cover elements.  Romance novels would be nowhere without the pair of entangled lovers to instantly cue in the reader to the torrid promise of the story inside.

Visual integrity - The colours, font, images layout and style need to be an integrated design.  A lack of visual integrity results in a design that may be discordant or incoherent, lacking the strength of message and recognition that you want the book cover to convey to readers.

Expression & Information - A cover needs to express what the book is about or unique and important elements of the story.  This may be the setting, the characters, plot, motvivaton or critical event (i.e. a murder, a prizefight, a fishing trip etc).

Differentiation and Emotion - The cover needs to strike a balance between the recognizable cover elements that readers are familiar with, and provide an emotional appealling point of differentiation - something that makes that particular cover stand-out from the twenty others surrounding it on the bookshelf.

Ideally all of the above elements are integrated into your design to ceate a compelling and interesting whole that readers will find impossible to resist.

So what covers work?  As noted, everyone's tastes are very subjective.  Here's  short sampling of several that stuck in my memory:

Looking for more insight or info on what type of covers work?  Five minutes on Google uncovered a vertiable cornicopia of book cover information.  For starters, visit The Book Cover Archive for a terrific compilation of exceptional book design covers.

For a self-publishing writer, the best approach would be to examine and analyze covers from your genre, ideally bestsellers or similar books that generated buzz, and see what elements of their covers worked for you.  Breakdown what elements worked for you and why, and try to see how the cover designs attracted your interest or attention (i.e. colour, typeface etc.).  Once you have an idea of what approaches seem to generate the more positive response, you can start to think about what your cover needs to reflect.

Then tell your designer.