Which C.S. Lewis book was adapted from his wartime radio broadcasts?

Mere Christianity was adapted from C.S. Lewis’s wartime radio broadcasts. The talks were delivered by the BBC between 1941 and 1944 and later revised and collected as a book.

Lewis’s broadcasts addressed basic Christian beliefs in language intended for a broad British audience during the Second World War. He did not present them as a defense of one particular denomination. Instead, he developed arguments about morality, human nature, Christian doctrine, and the practical meaning of faith.

The finished book combines material from Broadcast Talks, Christian Behaviour, and Beyond Personality. Its title refers to the shared core of Christianity rather than to a separate church or denomination. A common mix-up is to identify The Screwtape Letters as the broadcast book; although that work was also connected with wartime religious publishing, Mere Christianity is the collection directly derived from Lewis’s BBC talks.