I am a sucker for books about Narnia. Planet Narnia by Michael Ward (another Kindle impulse I wish I owned non-digitally) reshaped the way I read the Chronicles. The Magician's Book: A Skeptic's Adventures in Narnia was less revolutionary, but still contained much food for thought and plentiful insights for lovers of C. S. Lewis's creation.
Like many of us, Laura Miller fell head over heels in love with Narnia as a child, but became disillusioned as an adolescent when she recognised the 'Christian propaganda' embedded in the stories. But as an adult, she has returned to the books with a more thoughtful eye and acknowledged that they can offer joys and wisdom beyond that obvious 'message.' There is a lot of material here about Lewis and Tolkien, their friendship and the relationship between their respective works and beliefs -- probably slightly more material, if I'm honest, than I really needed (not a fan of Middle Earth); but I did learn a lot and the discussion was illuminating.
I'm going to keep my eye out for a hard copy.