What 1952 book by C.S. Lewis presents Christianity through a series of radio talks?

Mere Christianity is C.S. Lewis's 1952 book based on radio talks about Christian belief.

The work grew out of broadcasts Lewis delivered for the BBC during the Second World War, beginning in 1941. The talks were intended for a broad audience rather than for specialists, and Lewis presented arguments about morality, human nature, and core Christian doctrines in accessible language. He revised the broadcasts before they appeared in book form.

The title refers to what Lewis regarded as the shared central beliefs of Christianity, rather than to one particular denomination. It is not a novel and should not be confused with The Problem of Pain, another apologetic work published in 1940. Mere Christianity became one of Lewis’s most influential nonfiction books and remains widely read in discussions of Christian apologetics.