Which C.S. Lewis book explains Christianity through radio talks first broadcast during World War II?

Mere Christianity explains Christianity through radio talks first broadcast during World War II.

Lewis delivered a series of BBC radio talks between 1941 and 1944. The talks were aimed at a broad audience and presented arguments about morality, belief, and Christian doctrine in accessible language.

The material was later revised and collected in book form as Mere Christianity. The title refers to the shared core of belief among major Christian traditions rather than to a separate denomination. The book became one of Lewis’s most influential works of Christian apologetics.

The Problem of Pain and Miracles are also major Lewis apologetic books, but they were not the title of the wartime radio series. A Grief Observed was written much later, following the death of Lewis’s wife, Joy Davidman, and has a very different subject and tone.