I read this book first in high school, and have re-read it twice since then, each time liking it more. It is not a simple read, but well worth the time and effort. The ideas are strongly related to the author's faith (he was a pastor), and the elements of fantasy are used to relate the spiritual journey of the main character. At the same time, the story is a lot richer than a simple allegory, and the characters have a personal draw that is lacking in such Christian tales as "Hinds Feet on High Places."
This book gives one a lot to think about, with many different scenarios and themes presented in swift succession. Because it is older and fairly obscure, I find it more engaging to the imagination since it doesn't use a lot of the popular symbolism and euphemisms that make it easy to gloss over so many fantasy stories. Read this book slowly for the full emotional impact, because there's a lot of depth to it.
Didn't like it at all; couldn't finish the book. Fans of C.S. Lewis will like it though.