Beyond Arthur Conan Doyle, my favorite mystery writer is Dick Francis, just ahead of Agatha Christie, Dorothy Sayers, and Elizabeth George. I mention it because I'm in the middle of a Francis kick, one of those two-month periods when I read five or six of his books. I thought
For Kicks was especially good, but I was blown away by a basically forgotten mid-period book called
Banker. I think it may even be out of print, but it's worth getting your hands on.