I will pick up a book because of its cover, but I confirm with the description, reviews, and a bit of the inside whether or not it's for me. I like sophisticated/artsy covers but I don't like overly pretentious writing, so it's a bit of a trick. My most recent discovery with this method was John Danielle's books. It was the Devil House cover that got me interested. Ironically I enjoyed this two earlier novels much more.

I think Curtis Sittenfeld is the author for me who is most betrayed by her marketing/covers. She's written some killer literature that gets marketed as chick lit, which is a fine genre, but her books surpass that.