Which CS Lewis fiction have you read? Till We Have Faces is the best IMO and few people seem to read it. I also like Out of The Silent Planet and That Hideous Strength, although not the middle book of that trilogy, Perelandra. The Screwtape Letters and The Great Divorce are pretty good too.

I am not sure Tolkien's books are accurately described as children's books. The Hobbit perhaps, but not the Lord of The Rings IMO.

I started That Hideous Strength but did not get far. I'll put the others on my list!