What was the title of C.S. Lewis’s 1943 book about Christian belief?

C.S. Lewis’s 1943 book about Christian belief was Mere Christianity.

The book grew from radio talks Lewis delivered for the BBC during the Second World War. Those broadcasts were later revised and published in book form. Lewis aimed to explain shared Christian beliefs rather than defend one particular denomination, which accounts for the title.

Mere Christianity is arranged in three major sections: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” and “Christian Behaviour.” A later section, “Beyond Personality,” discusses the Christian understanding of the Trinity and spiritual life.

The work is not a novel and does not present a complete history of Christianity. It is a popular apologetic text, written for general listeners and readers. The broadcast origins also explain its direct, conversational style and its emphasis on clear examples.