Before reading That Hideous Strength I never realized how badly Lewis wanted all the myths to be true, King Arthur and Merlin, the Greek gods, Atlantis, even Father Christmas. It makes you wonder if his outspoken defense of Christianity wasn't just an attempt to find a set of myths he could believe were real.
Lewis' Space Trilogy is not science fiction by any reasonable definition of the term, it is a metaphysical fantasy. Lewis had no use for science and equated it with black magic at ever opportunity. If you can get past Lewis' intense loathing for anything to do with progress and the modern world, and his extremely patronizing attitude toward women, That Hideous Strength is actually an entertaining satire.
You can't help but wonder that if Lewis had continued writing in this vein, after venting all the bile he let out in this novel, he might have written some interesting modern fiction. Instead he switched to writing children's fantasy, and I think both he and the children's fantasy genre were improved by his choice.