The Rule of Four

This was an excellent book. When I read the Da Vinci Code, I was fascinated by the idea of codes in works of art. This goes one better. The code is in a Renaissance book called the Hypnerotomachia Poliphili. The story is wonderful, with believable, three dimensional characters. The neatest part of it is that there really is a Hypnerotomachia Poliphili. It was published in 1499. No one knows who wrote it. You can read more about it (and the book itself) here.