I think Lewis was so compelling because, first, he was incomparable at evoking "joy" as he defined it. Whatever idea and yearning for "heaven" I ever had came from Narnia. Second, I think he had an intuitive -- not theoretical -- grasp of psychology -- he was one of those people who reads his own mind so well, he knows a good deal about how all human minds (and wills and emotions) work.The bickering of the children in The Magician's Nephew, Eustace's redemption in Dawn Treader, the seeds of human hatred elucidated by Screwtape -- and above all, the parental love turned to jealous gall in Till We Have Faces -- his greatest imaginative leap and rendition of the romance of the soul --have a kind of easy, intimate verity that give his spiritual dramas life.Meanwhile, the former Archbishop of Canterbury Rowen Williams, who just wrote a book about CSL, seems a bit confused about Lewis' core concept of joy.
At the same time, when it came to doctrine and apologetics, I think he was an unwitting sophist -- an honest sophist, if that makes any sense, because he fooled himself first...
He's a democrat (small d, believer in democracy) by default, of the Churchillian school that democracy is the worst form of government except for all the alternatives. His own formulation was that democracy is necessary because human corruption means that no individual or small group can be trusted with power. That's true, and salutary. What Lewis lacked was any sense that participating in political life is part of what makes us fully human -- and the corollary, that a people's meaningful participation in politics could permanently advance human welfare. Strange, for a man steeped in Greek literature -- no sense that man is a political animal.
And I've got beef with Lewis's idealization of the past and pooh-poohing of human progress.
But I do love and honor his heavenly imagination.