Which C.S. Lewis book presents Christianity through a series of radio broadcasts?

C.S. Lewis’s book presenting Christianity through radio broadcasts is Mere Christianity.

The work grew from a series of talks Lewis delivered for the BBC during the Second World War. The broadcasts were aimed at a broad British audience and explained basic Christian ideas without focusing on the differences between particular denominations. Lewis later revised and expanded the material for publication.

Mere Christianity is organized into four parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behaviour,” and “Beyond Personality.” The book’s title refers to the central beliefs shared by historic Christian traditions.

The work is sometimes mistaken for The Problem of Pain, another major Lewis book about Christianity. That earlier volume is a sustained argument about suffering and divine goodness, whereas Mere Christianity originated specifically in wartime radio talks.