Meh. No matter how many beers and smokes CS lewis had, it's still Christian allegory. Movies alway steer away from the books they're based off of. Childrens movies around Christmas time always focus heavy on family. The author is just disgusted with it in Narnia because she hates Christianity.
Laura Miller (the persons who wrote this article), wrote this book
Excerpt from the first chapter of the book:
"I began The Magician's Book hoping to explain not only why but how it is still possible for me to love these books, despite the biases and small-mindedness they sometimes display, despite often feeling that I wouldn't have much liked the man who wrote them"