The cool thing about this book is that it makes you ponder the nature of good and evil without hitting you over the head with any moral message. Like real life, it's all about free choice. Unlike real life, this battle between good and evil involves notorious historical characters as well as God and the Devil their ownselves instead of priest-and-or-rabbi surrogates.
Oh, yeah. It's a pretty good story. The author takes license with history, it really didn't happen this way, but it could have. That is, if you believe in God and the Devil. Which the hero doesn't. Even after he has met both.