Book covers are just as important to attracting a reader, as the summary on the back. The first thing that attracts a reader is the cover. I pick up a lot of books because I like the cover. Covers hint at what the book is about. They are also pretty clear about what genre the book belongs to. The covers usually warn me away from genres I don't like. For example romance novels have a man in a woman, usually in a ridiculous pose, with wind blowing in their faces and bronzed skin, revealed by their lack of clothing. Its usually the men who get their shirts taken off on these covers. Eye candy for the middleaged woman, whose love life isn't quite that exciting.

Generic Fantasy books have covers with combinations of mythical beasts, medieval clothing, swords and sparkly magic items. Not every book falls into the solid idea of the genre and their covers usually reflect that.

Mystery books tend to have vague images of streetlights, doors, keys, and other random objects that show up in the mystery. It easy to tell if the mystery revolves around murder because the publishers can't help but add a splash of blood to the cover.

The covers that make me laugh are the older sci-fi space books. All of the technology is really jaggedy like the insides of a computer; and everyone wearse spandexy uniforms in vibrant colors. Recently we portray technolgy as clean cut, like the style of the ipod. Its like Eva vs. Wallee.

I guess what I'm trying to say is the publishers make it easy for us to see what we're looking for. They have mad marketing skills. (or they could just have a thing for cheesy cover art)