Which C.S. Lewis book presents Christianity through fictional conversations among demons?

The Screwtape Letters presents Christianity through fictional conversations among demons.

Published in book form in 1942, The Screwtape Letters consists of letters from Screwtape, an experienced demon, to his inexperienced nephew Wormwood. Screwtape advises Wormwood on how to tempt and mislead a human known only as “the Patient.” The structure lets Lewis examine ordinary moral and spiritual weaknesses from an intentionally inverted perspective.

The book was first published serially in the Anglican newspaper The Guardian during 1941. Lewis’s satirical method made abstract ideas about temptation, pride, distraction, resentment, and self-deception vivid for general readers.

The letters are not a conventional account of Christian doctrine, and Lewis warned that the demonic viewpoint could be spiritually uncomfortable. The book is often confused with The Great Divorce, another imaginative work, but that later book uses a bus journey between Heaven and Hell rather than correspondence between demons.