I have written an article for the November Evangelical Times on C S Lewis, which you can preview on the website. The whole edition looks like it's worth getting I'm sure.
Back in my salad days when I was green in judgement, some 20 or more years ago, I remember telling a congregation, by way of application, not to bother to read anything by C. S. Lewis. I did not say he was of the devil or not a Christian, as some would maintain, but I thought there were better things to read. I remember a young man challenging this statement, which I defended then but would now want to nuance quite a bit. Like all generalisations, including this one, it was inaccurate. But what prompted such a swingeing generalisation?