The obvious option for the aesthete is to organize by color. Categorizing by color always creates order in a cluttered situation. (Banana Republic sale section, anyone?) While it's not the most efficient way to access your library (unless you know the color of your books by heart), it's definitely the way to make your visitor's jealous!
So what if it takes you an hour to find your copy of War and Peace? At least you can look at your bookshelf without flinching.