Which C.S. Lewis book presents seven radio talks about basic Christian belief?

Mere Christianity presents C.S. Lewis's radio talks about basic Christian belief.

The talks were broadcast by the BBC during the Second World War, beginning in 1941. Lewis spoke in a direct, conversational style intended for a broad audience rather than only for theologians. The broadcasts were later revised and collected in book form.

The work explains ideas such as morality, human nature, repentance, and Christian belief. Its title refers to the shared core of Christianity rather than to one particular denomination. Lewis aimed to discuss common Christian convictions before addressing denominational differences.

The book is sometimes mistaken for a conventional autobiography or a novel. It is instead a work of Christian apologetics, meaning an argument or explanation offered in defense of religious belief. Its origins in radio talks explain its accessible tone and clear structure.