@Cosmic Castaway
C.S. Lewis really is a great author. I liked his The Screwtape Letters shorts which are pretty good. And I'm almost done with Mere Christianity.
It does explain plain and simple what christianity is all about in terms of it's belief system, the difference between a material view of the word and the spiritual, issues like charity, marriage, war, pride,etc. The core of his essay, however, is indeed a sharp and detailed criticism on what is considered pseudo-spirituality, nihilism and moral relativism. He also debunks several myths about all the alleged benefits of becoming of Christian denomination.