I am not certain if I have ever mentioned that my years in college were spent getting a degree in advertising and marketing. I don't know if it is for this reason or just common sense, that I know the phrase "You can't judge a book by its cover," is a phrase that needs rebutted. You can judge a book by its cover; however, that is not to say that you have judged it fairly.
If I arrive at a bookstore without any recommended purchases in mind, the first things I do are beeline for my favorite genre then start browsing the covers. If the cover appeals to me then I pick it up to read the blurbs. It is a game of dating. There has to be an initial attraction before the getting to know you normally commences. Maybe the initial interest comes from a friend's recommendation. Like being setup. But how often, or how willing are we to blind date our books? Just go to your favorite genre grab a book that has its spine toward you and purchase it cover unseen.
What do you look for while you are prowling the book store aisles?
What makes your heart quicken?
How do you make your pick?