What was the title of C.S. Lewis’s 1942 book defending Christianity through fictional correspondence?

C.S. Lewis’s 1942 book defending Christianity through fictional correspondence was The Screwtape Letters.

The book consists of letters from Screwtape, a senior demon, to his inexperienced nephew Wormwood. The correspondence reverses the usual perspective: readers observe human temptation, distraction, pride, and spiritual confusion through the advice of Hell’s bureaucratic administrator.

Lewis published the work in 1942, during the Second World War. Its satirical form allowed him to discuss moral and theological ideas indirectly, while the demonic narrator’s self-interest exposes the habits he recommends. The book was first published in serial form in the Anglican newspaper The Guardian before appearing as a volume.

The Screwtape Letters is often grouped with Lewis’s apologetic works, but it is not a conventional treatise. The Great Divorce uses an allegorical journey, while Till We Have Faces is a mythic novel. Those books share themes with it but are different works.