Tactically, the cover sells the back cover, the back cover sells the flap and by then you've sold the book. If those steps end up selling a book that the purchaser doesn't like, game over. So you have to be consistent all the way through and end up creating a conversation after the purchase. Books are better at creating conversations than most products (when was the last time you talked about a pool cue), but there's lots of opportunity here, no matter what you make.
The whole post really resonated with me, because just last night I was at my book club, and it was my turn to choose books for our next meeting. One of the books I had brought with me I picked solely for the beautiful cover. Of course, when I was at Borders picking it out, I did flip it over to the back flap (more great design--hello? I was so not putting this book down at this point), and then I read the inside flap, which completely intrigued me. The book? Little Bee, by Chris Cleave.
How could you just walk by this book? The elegant script, the spot varnish, and the great type--that's what grabbed me WAY before I knew what this book was about. And yes, I know I'm a designer--that stuff should grab me--but for anyone, I think it's a hard book not to notice.
When I presented it to my club, I told them point blank that it was a book chosen for the design. Of course, once I read the inside flap to them (I didn't even start on the back cover design, I think I was boring them to tears with my font talk), there was no question on what we were going to read next. I think it will, but I'm anxious to see if the plot holds up to the spectacular cover design.