It's no accident that the first mass-production of copies of the Bible in Europe coincides with centuries of religious upheaval. Before the invention of the printing press, every copy of a piece of writing was usually so obviously unique that the idea of owning a definitive 'edition' of something would have seemed absurd.

Printing took the ability to reproduce Christianity's central text out of the hands of the rich, the powerful and the deeply invested and placed it in the hands of a wider public – a process those familiar with Walter Benjamin's essay 'The Work of Art in the Age of Mechanical Reproduction' will no doubt recognise. Wouldn't it be nice to think that, fast-forwarding a century or two, we'd find the culmination of this process in a literary life as even-handed and unbiased as the democratic society of which it forms a significant part?

Perhaps a quick sample is in order. Look at your bookshelves and pick out all the poetry books (preferably produced in the last 10 years or so) you can find. The fact that you will instinctively distinguish books of poetry from other sorts of books notwithstanding, try comparing some of the volumes without any reference to their contents and I'll do the same here.
 
The first thing you'll probably notice is that, once you put the anthologies and synoptic volumes aside, most of the remaining books will be paperbacks of roughly the same thickness. The main text will probably carry a uniform font, and the paper will likely be of relatively high quality. Now look at the covers, which will probably be printed on the same material across the board – matt-finish card, nothing too shiny, printed in colour with an image of something interesting but not obviously or immediately related to the title.
 
To me, that sense of uniformity is striking. And before you start arguing about how it's the contents that matter, think about it this way: when you go into a shop to buy a book of poetry, how do you know what to look for? And why are you so fond of your collection of Faber two-tone covers? These books, after all, aren't being given away, and their covers are part of a sales pitch. These books want to look like poetry, and in so doing deepen your implicit idea that you know what poetry actually is. You may wish to participate in that idea, or believe it to be the best idea you could presently hold, but unless you scrutinise it you're putting yourself in the wrong place: it's not you judging the cover, it's the cover judging you.
 
When people say 'I don't judge a book by its cover', they're usually saying 'I don't consciously judge a book by its cover'. You can put that judgement out of sight but you'll never put it out of mind. We live in a highly developed and sophisticated visual environment, so it's inevitable that we should judge by appearances. And the more ready we are to recognise its influence, the better we will be at negotiating our way through it.