C.S. Lewis and Narnia for Dummies is a great book!! It tells about C.S. Lewis conversion to Christianity, has a chapter on The Great Divorce, and has a table on weaknesses of the heroes(?) in Narnia.
Chapter one is C.S. Lewis` Gift To The World, about his writing skills, while chapter two is Getting To Know Jack, about C.S. Lewis himself.
Oh, and at the beginning there is a cheat sheet! (Did you know the emperor-over-the-sea was a symbol of God the Father? Or a good line to use at a party is "_____'s my name. But it doesn't matter if you forget it, I can always tell you again."?)
You can buy this book full of goodness on Amazon!