C.S. Lewis published Mere Christianity as a single book in 1952.
Mere Christianity grew out of radio talks Lewis gave for the BBC during the Second World War. The broadcasts were delivered between 1941 and 1944 and were intended to explain basic Christian beliefs in accessible language to a broad British audience. Lewis later revised and combined the talks into book form.
The 1952 volume brought together material from three earlier works: Broadcast Talks, Christian Behaviour, and Beyond Personality. Its title refers to the shared core of Christian belief rather than to one particular denomination. Lewis organized the work around moral law, Christian belief, and practical Christian conduct.
The book is often confused with the dates of the original broadcasts, which came first. The radio talks began in 1941, while the unified book appeared in 1952. Mere Christianity became one of Lewis’s most widely read religious works and helped establish his reputation as a public Christian apologist.