What is a mystery, anyway?

While deciding what to include in my Times Book Review post, I started thinking about how we're defining "mystery" for the purposes of this blog. Basically, anything goes. I'm using "mystery" as a catch-all for detective novels, crime fiction, thrillers, suspense, romantic suspense, etc. If the solution to a crime (or possibly another big puzzle) is at the center of a book, show, or movie, it counts. Of course, this definition may have to be refined as we go along, but I think it will work for now.