This web site has amazing book covers that will explode your sales! Here's some useful information about book covers. 

A book cover is a protective covering that binds pages of a book. They can be hardcovers and paperbacks. In addition, there are dust jackets, ring-binding covers, and other types that have an artistic flair. The Arts and Crafts and Art Nouveau movements in the late twentieth century ignited a renaissance in book cover design that spread through the growing book industry.