Which C.S. Lewis book was adapted from his BBC broadcasts about Christianity?

Mere Christianity was adapted from C.S. Lewis’s BBC broadcasts about Christianity.

Lewis delivered the first series of talks in 1941, followed by additional broadcasts in 1942 and 1944. The talks were intended for a broad wartime audience and explained shared Christian beliefs in accessible language rather than focusing on one denomination.

The broadcasts were later revised and published in book form. Mere Christianity is organized around moral law, Christian beliefs, and the virtues and practices of Christian life. Its title refers to what Lewis considered the common core of historic Christianity.

The book is not a transcript of one continuous lecture series in its final form. Lewis edited and rearranged the material, and later editions made further changes. It is therefore distinct from The Problem of Pain, another major work of Lewis’s Christian apologetics.