Which C.S. Lewis book presents Christianity through a fictional demon’s letters?

The Screwtape Letters presents Christianity through letters written by a fictional demon.

Published in 1942, the book consists of correspondence from Screwtape, a senior demon, to his inexperienced nephew Wormwood. Screwtape offers advice on how to tempt a human patient away from faith, virtue, and clear thinking. Lewis uses the reversed viewpoint to expose habits and moral weaknesses that people might otherwise overlook.

The book began as a series of letters that Lewis read on BBC radio during the Second World War. It was later published as a book and became one of his best-known works of Christian apologetics. Its satirical structure allows Lewis to discuss pride, distraction, social pressure, prayer, and spiritual growth indirectly.

The letters are fictional, not a record of alleged supernatural communications. Screwtape’s professional title and Wormwood’s assignment are narrative devices that make the moral argument memorable.