Alan Jacobs, in an interview with Ken Myers, as recorded in back matter of Jacob’s excellent book, The Narnian: The Life and Imagination of C. S. Lewis [(HarperCollins, 2005), page 349,] said:

“…almost everything that Lewis really cared about and that he deeply believed in, almost everything that he thought was vital for us to know, no matter how scholarly, no matter how intellectual, found its way somehow into the Narnia books—to a shocking degree, actually. You wouldn’t think that he would be able to get all that stuff into a series of what are, after all, relatively brief books for children, and yet he did.”