Which C.S. Lewis book collects material from his wartime radio broadcasts?

Mere Christianity collects material from C.S. Lewis’s wartime radio broadcasts.

The broadcasts were delivered for the BBC during the Second World War, beginning in 1941. Lewis spoke about basic Christian belief in language intended for a broad public audience, and the talks were later revised and assembled into a book. Mere Christianity was published in book form in 1952.

The work is organized around common Christian ideas rather than the distinctive doctrines of one denomination. Its early sections discuss morality and the idea of a shared moral law; later sections develop Lewis’s account of Christian belief and conduct.

The title is sometimes mistaken for a general biography or a novel, but it is a work of Christian apologetics. The Problem of Pain is another apologetic book by Lewis, while Surprised by Joy is autobiographical. Mere Christianity became one of his most widely read nonfiction works.