Planet Narnia reads a bit like a PhD thesis. (And may well have been exactly that in fact. I haven’t done any research to find out.) But if you like your books full of references and with a very precise structure you are in for a treat. And it is a double treat if you like a rather tortured academic style of writing.
My three favourite twentieth century English authors are Orwell, Tolkien and C.S.Lewis. It isn’t a perfectly equal trinity though. I think Orwell and Tolkien are writers of huge genius who will be read for centuries to come. Lewis I like a lot and enjoy reading, but he isn’t really in the same category. He can certainly write well and has lots of interesting ideas, but I think he is very much of his time and will get steadily less relevant as the world changes. He also got a lot of his ideas from the other two. This doesn’t diminish how much fun you get from reading him. But originality always commands more respect than derivation, no matter how skilfully done.