To me, Narnia was a perfect series for the un-cluttered mind of a child. It was easy to recognize the Christianity behind the writings, but unconcerned about the "theology" of it, the inconsistencies didn't bother me. A child could "get" the moral without being clubbed over the head with it.
As an adult, I have greater appreciation for the "theology" of Tolkien and the years of effort he put into making sure it was correct. The Christianity in it isn't so easy to decipher, until one steps back and thinks about it. On the first read, I missed many of the connections or "knots" in the rope as Tolkien described them. But as I read about it, listened to podcasts on the subject and then discuss the books with my daughter, they become apparent.
It is interesting to look at the Narnia series as Ward does here, looking deeper and making the connections that weren't obvious before. Seems like great literary works offer that deeper meaning every time they are reviewed and studied, like the greatest literary work of all time, the Bible. But one must be careful not to have the theory formed before the facts are presented (to borrow from Sherlock Holmes) because that can lead to facts being twisted to fit the theory.
Not saying that Ward does that with here, but just saying.