Like just about everyone else, I have read The Chronicles of Narnia many times, starting from the age of seven until now. My literary sensibilities are quite different now than when I was seven, and it is to the books' credit that I keep on finding new things to appreciate in them. This is especially important given the fact that some of the book's more heavy handed, allegorical passsages were pretty obvious to me from about the age of ten, and yet there are reasons that I continue to return to these books. I don't think I am alone in this, since these books were touchstones of the development of the last few generations, including those who went on to become pagan anarchists or whatever.
A few weeks ago, while reading The Voyage of the Dawn Treader, I realized the reason that C.S. Lewis manages to capture the imagination of people who don't subscribe to his religious or moral beliefs. In the end of the book, he is describing the final voyage of the ship The Dawn Treader to the end of the world, and the effects of drinking the sweet seawater on the sailors, how it made them feel light, energetic and relaxed, and gave them the ability to stare directly into the sun. At an older age, I realized something about this passage that I would never have realized at a younger age: that this was a real description of a mystical experience. And I think it is these imaginative, authentic descriptions of mystical states and places that are what draws me back to the books.
On the other hand, the books do have many passages where Lewis' religion tends away from the mystic. Not only do the many religious and moral messages in the books tend to be different from what most readers would believe, they are also told, from a literary viewpoint, rather badly. Lewis was a heavy-handed writer at times. And I think it is these passages that may unfortunately stick in some reader's memories, and turn people off from the books. It also, of course, depends which one of the Chronicles are being read: The Voyage of the Dawn Treader, The Magician's Nephew and The Last Battle have some of the more mystical and fantastic passages, while the other books tend to have much more preachiness.
The question is, how do Lewis' moral and mystical teachings relate? Honestly, answering this question would have to involve me knowing a lot more about both the history of Christianity and Lewis' personal and intellectual background than I do know. Even with that, these questions probably don't have a very pat answer, since the dynamic between conventional morality and mysticism and theology in any religion is often a problematic one. Was Lewis basically a mystic, or was Lewis basically a conventional moralizer? I don't believe that question can be answered. I can say that purely based on the books themselves, the transition is somewhat awkward. The mystical passages are attractive and interesting, while the moralistic passages are...somewhat stiff.
This is obviously a complicated question, and the thoughts that I have jotted down here are just an introduction to the complex issue of the purpose of religion, how that purpose interacts with the artistic expression of religion, as well as the specific details of C.S. Lewis' beliefs, as expressed in these books.