Which Christian radio-broadcast book by C.S. Lewis was first published in 1952?

Mere Christianity is the C.S. Lewis book first published in 1952 from his wartime radio broadcasts.

Lewis delivered the original broadcast talks for the BBC during the Second World War, beginning in 1941. The talks were later revised and assembled into a book, with the title Mere Christianity referring to the core beliefs shared across historic Christian traditions rather than to one denomination.

The 1952 volume combined material from Broadcast Talks, Christian Behaviour, and Beyond Personality. The work is often confused with The Problem of Pain, which was published in 1940, before the broadcasts. Mere Christianity became one of Lewis's best-known works of Christian apologetics and helped make his arguments accessible to a broad radio audience.