Which C.S. Lewis book adapted his BBC radio broadcasts into Christian apologetics?

Mere Christianity adapted C.S. Lewis’s BBC radio broadcasts into a book of Christian apologetics.

Lewis delivered the broadcasts during the Second World War, beginning in 1941. The talks were intended for a broad British audience and explained central Christian ideas in accessible language rather than presenting a detailed defense of one denomination.

The book was assembled from three broadcast series: “The Case for Christianity,” “Christian Behaviour,” and “Beyond Personality.” The title refers to the shared core of historic Christianity, not to a separate church or denomination.

Lewis’s discussion of morality, belief, and Christian character made the book influential among readers interested in religious philosophy. It is sometimes mistaken for a memoir or a novel, but it is primarily a work of apologetics and religious argument.