Inside Google Books: Judging a book by its (pretty) cover

"Library books often contain beautiful drawings and illustrations. Unfortunately, their book covers can often be dark and plain, hiding all this wonderful content from unsuspecting eyes. Over time, we've tried a bunch of different approaches for getting better covers, for example, using the book's title page or recreating a simple book cover by featuring the book's title and author. Finally we hit upon an idea that we like -- why not surface the illustrations inside the book to be its front cover?"