One point of his conversion that I find quite interesting.
"Thus in the very act of trying to prove that God does not exist - in other words, that the whole of reality was senseless - I found I was forced to assume that one part of reality - namely my idea of justice - was full of sense. Consequently atheism turns out to be too simple. If the whole universe has no meaning, we should never have found out that it has no meaning: just as if there were no light in the universe and therefore no creatures with eyes, we should never know it was dark. Dark would be a word without meaning."
The decision to believe in God is still a decision, this "proves" nothing. Anything that can come of intelligence and order CAN also come of randomness. As I've said before, God isn't going to force you to believe in him, you are welcome to worship chaos and meaninglessness. Down that path, the highest moral certainly is "what feels good". You may dress it up as "what feels good for the most people", but it is still a human determination about "pleasure". However, the Lewis formulation on meaning is still a nice try.
In chapter 4 he makes one of the best statements of not only why Christ had to die, but why nobody is "saved by their own decision".
"Remember, this repentance, this willing submission to humiliation and a kind of death is not something God demands of you before he will take you back and while he could let you off of if he chose: it is simply a description of what going back to him is like. If you ask God to take you back without it, you are really asking him to take you back without going back. It cannot happen. Very well then, we must go through it. But the same badness which makes us need it makes us unable to do it."
He then goes through a discussion of how God himself is unable to help us in his God state; ...
"But supposing God became a man - suppose human nature which can suffer and die was amalgamated with God's nature in one person - then that person could help us. He could surrender his will, and suffer and die, because he was man; and he could do it perfectly because he was God.".
The chapter that hits home to me the most was chapter 8, "The Great Sin". ...
"There is no fault which makes man more unpopular, and no fault which we are more unconscious of in ourselves. And the more we have it in ourselves, the more we dislike it in others.
The vice I am talking of is Pride or Self-conceit: and the virtue opposite to it in Christian morals, is Humility. ... According to Christian teachers, the essential vice, the utmost evil is Pride."
He goes on to talk how it is of course pride that makes Satan, and of course one can't be human and be without some of this most grievous of sins. In the modern world, it has become very common to refuse to acknowledge God at all, but even for those that would like to do so, removal of pride is a great gift.
"The real test of being in the presence of God is, that you either forget yourself altogether or see yourself as a small, dirty object. It is better to forget about yourself altogether". There isn't a lot to be added to that.
I'm not going to go on any more. I know it is a book that has changed many lives for the better, and no doubt made some more angry and bitter as well, but that is certainly not the intent of it. It is with certainty a "great book" in that it takes on the questions of most fundamental meaning to a human. Is this all there is? C.S. Lewis makes a marvelous case that it is only the beginning.