Be prepared to waste a ton of time on this site. The Book Cover Archive features over 800 examples of excellence and creativity in book design. And one of the coolest parts about the site is that you can choose how you browse the covers. If you want to narrow things down a little bit more, you can search by a particular designer or illustrator, genre, author, publication date and more.
It was created by Ben Pieratt of General Projects and Eric Jacobsen of Whisky Van Gogh Go “for the appreciation and categorization of excellence in book cover design.”