Yes, Inwe, there are very definite religious allegories in the books, but I don't think we can discuss them here.
Rest assured I'm not going to "discuss" them here, only a comment! Lewis did say (or write in a letter somewhere) that all of his Narnia books -- and indeed his Space Trilogy books as well -- were not written in order to be religious allegories. Like Tolkien, he didn't like "allegories" very much. Rather, he made a clear distinction between his stories and allegory (in which each thing or person in a story represents or correlates directly to another thing, often very obviously, and often in order to teach some point, and in fact the author may go to great pains to UN-disguise the allegory as much as possible). I'll have to look it up, but the gist of it is that Lewis said he imagined what might happen if his God had actually created other worlds.... whereas he thinks of allegory as merely a thinly disguised way to talk about our own real world. In this sense, you will find Lewis's idea of God in his books, but the rest of the worlds he imagines are NOT meant to correspond directely to things in "our" world.
It's possible to say that Lewis wrote "theology fiction" where his books are related to theology in the same sense that "science fiction" is related to science. (That is to say, both genres imagine what might happen IF certain imaginary things were true in addition to most of what we already know or believe about either discipline).
I hope mentioning this isn't breaking the "rules", (I didn't think so, since it's about what Lewis' process of writing)