One of the most influential Christian books of our time is “Mere Christianity” by C.S. Lewis. The book began as a series of BBC radio talks during World War II. The BBC wanted someone to address serious issues of the Christian faith during the war. Before the talks, C.S. Lewis was a little-known Oxford professor. But the BBC broadcasts catapulted Lewis into a prominent defender of the Christian faith.
Ironically, after these broadcasts the BBC was forever recruiting Lewis to do more broadcasts and he nearly always declined because of the hassles of travel and writing for radio, and because of his full schedule.
This is not a great book but I find Lewis forever fascinating.