Which C.S. Lewis book presents his account of Christian belief in expanded form?

Mere Christianity presents C.S. Lewis’s account of core Christian belief in expanded book form. It developed from radio talks broadcast by the BBC during the Second World War and was published as a book in 1952.

Lewis’s broadcasts were first delivered in three series between 1941 and 1944. He aimed to explain shared Christian ideas in accessible language rather than defend one particular denomination. The book’s title refers to the common core of belief that Lewis believed united major Christian traditions.

The work is arranged in four parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behaviour,” and “Beyond Personality.” Its discussions include morality, faith, forgiveness, and the Christian understanding of God and human transformation.

Mere Christianity is often confused with The Problem of Pain, another major Lewis work about Christianity. The Problem of Pain focuses especially on suffering and the problem of evil, while Mere Christianity offers a broader presentation of Christian doctrine and practice.