Mysteries appeal. Especially if well written.

Have you ever read Ellis Peters' Brother Cadfael mysteries? Excellent characters, intriguing plots, and a fascinating historical setting-- England during the 12th century, when King Stephen and Empress Maude/Matilda were fighting over the throne. Brother Cadfael is one of my favorite literary characters, right up there with Lord Peter Wimsey.
Speaking of Lord Peter, all of Dorothy Sayers' mystery novels are wonderful.
I also recommend Anne Perry's Victorian mysteries, which are a lot of fun and very well written.