Did you know a book cover (not content) can sometimes be the determinant of whether or not a book sells? I know authors may feel disappointment that a visual aid could make or break their books, but it's one of those realities.
Here is what I know about great book covers:
Sex always sells. It is just the way it is and no use in fighting mother nature. So a compelling and sizzling sexual cover can do wonders to pique curiosity and sales.
Beauty sells though too. One of our authors was stuck on whether to go sexy or beautiful. She went beautiful on instinct and her book cover for Passenger from Greece was acknowledged with a finalist award.
Headline treatments can stand on their own. A compelling title combined with an interesting use of typography and white space can provide the tools for some fantastic book covers.
Mystery and intrigue provide the basis for great covers. Think about 50 Shades of Grey, a now iconic book cover. It had a lure of dark mystery about the tie and the hand on the tie.