Which C.S. Lewis book was adapted from his BBC radio broadcasts on basic Christian belief?

Mere Christianity was adapted from C.S. Lewis’s BBC radio broadcasts on basic Christian belief.

Lewis delivered the first broadcast talks during the Second World War, beginning in 1941. The talks were intended for a broad British audience and discussed morality, Christian doctrine, and the central beliefs shared by major Christian traditions.

The material was published in book form in stages. Broadcast talks became Broadcast Talks in 1942, followed by Christian Behaviour in 1943 and Beyond Personality in 1944. These sections were later revised and collected as Mere Christianity in 1952.

The title does not refer to a specific church denomination. Lewis used “mere Christianity” for what he considered the common core of Christian belief. The book is therefore different from The Problem of Pain, which was published in 1940 and focuses primarily on the problem of suffering and evil.