The book cover is unique in that the unit can be sent in the normal manner through the mail as a card, and instead of being discarded when received, it is usable as a book cover for different thicknesses of books particularly those of the paperback type. The undesirable picture and title on the outer cover will be hidden. The cover folds into post card form and is secured by a tab disposed in an end slot, the tab being usable as a bookmarker when the cover is applied to a book.