Which C.S. Lewis book collects his 1940s radio talks about Christianity?

Mere Christianity collects C.S. Lewis’s 1940s radio talks about Christianity.

The talks were broadcast by the BBC during the Second World War, beginning with a series in 1941. Lewis spoke in clear, conversational language about morality, Christian belief, and the central claims shared by major Christian traditions.

The talks were later revised and published in book form. Mere Christianity is divided into four parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behaviour,” and “Beyond Personality.”

The title does not mean a minimal or careless form of Christianity. Lewis used “mere” in the older sense of basic or essential. The book is an apologetic work rather than a full denominational theology, and it deliberately focuses on points of broad agreement among Christians.