Which C.S. Lewis book presents Christianity through fictional correspondence between demons?

The Screwtape Letters presents Christianity through fictional correspondence between demons.

C.S. Lewis’s book consists of letters written by the senior demon Screwtape to his nephew Wormwood. Their correspondence discusses how to influence a human being through habits such as resentment, vanity, distraction, and false humility.

The unusual viewpoint is central to the book’s method. Lewis does not present direct theological instruction in the voice of a preacher; instead, he lets demonic advice expose the weaknesses that Christian moral teaching warns against.

The work first appeared in book form in 1942 after being published as a series of letters in the Anglican newspaper The Guardian. It became one of Lewis’s best-known works of Christian apologetics and remains distinct from his nonfiction books of direct argument.