And did you pick up the book BECAUSE of the cover? Or were you going to read it anyway, and the cover was just serendipitous?
An example that comes to mind is Michael Connelly's A Darkness More Than Night. I love that title. It immediately sets a tone that strikes a chord with me. The story sounds interesting and having read Connelly before I know I like his writing. The cover is a yellow eye in the middle of all black. It does nothing for me. It's kind of obvious that even the publisher is expecting to sell this book off the name of the author more than the picture it shows.