Which C.S. Lewis book was adapted from his 1940s BBC broadcast series The Case for Christianity?

Mere Christianity was adapted from C.S. Lewis’s 1940s BBC broadcast series, including The Case for Christianity.

Lewis’s first broadcast series, The Case for Christianity, was transmitted in 1941. Additional BBC talks followed under the titles Christian Behaviour and Beyond Personality. Lewis revised the material and assembled it into the book Mere Christianity, published in 1952.

The resulting work is not a transcript of a single uninterrupted program. It is a shaped book that combines material from the different broadcast series and organizes it into a progression from moral law to Christian doctrine and practical Christian conduct.

The title is sometimes mistakenly applied to The Case for Christianity itself, but that was the title of the first radio series and also of an early book edition of its material. Surprised by Joy is Lewis’s autobiography, while The Four Loves grew from a separate broadcast series. The book’s enduring appeal comes partly from its direct, radio-friendly prose.