The NYT Book Review has a really nice little piece on what it takes to design a book cover for a bestseller.
How do you design a cover for a novel that must, to recoup the publisher’s investment, sell hundreds of thousands of copies — and sometimes more than a million? Very carefully, of course: books do get judged by their covers. “With fiction you only have a split second for the customer to decide whether a book looks interesting,” said Zan Farr, a buyer for Borders. Read the whole thing