As a kid the Christian overtones go right over your head.. as an adult they're a lot more glaring, and (to some of us), grating.
"Tolkien and Madeleine L'Engle wrote novels in a similar vein (that are also excellent children's books)."
I loved Madeline L'Engle as a kid, but tried to pick up A Wrinkle in Time recently, and couldn't bear all the Christian preachiness. Worked for me as a kid, though, and back then I had no idea that was in it. I guess that's saying something. But as an adult it's nauseating.