I recently bought a copy of Guy Kawasaki's The Art of the Start. Great book so far, but one of the first things I noticed was the comment on the back inside flap:
The front jacket was created by Adam Tucker, winner of a design contest sponsored by Guy Kawasaki. Please take off the book jacket to see some of the other entries from his fans on the reverse side.
That's right. The inside of the dust jacket features 70-odd submissions for cover designs. Each of them is completely different. Makes you realise not only how much variation there can be in a book cover but also just how different one's perception of a book can be depending on the cover.
They say you shouldn't judge a book by its cover. But have 70 alternative covers suggested to you and you pretty soon decide which make you want to buy the book and which don't.
For what it's worth, I think Guy picked the right cover in the end.