I have a simple rule: never touch a book whose title is a full sentence.

It's not obvious why it works so well. My working hypothesis is this: The writer had a message so important that even people who don't touch the book should get it. Where to put it? Cram it into the title. The problem is, if it fits in the title, it doesn't need a book, does it? Furthermore, anybody who's that sure his idea is so important is probably wrong about a lot else. Even if the book says more than the title, we have been given a good reason to distrust it before we open it.