What was the title of C.S. Lewis’s 1942 Christian apologetics book framed as letters from a demon?

The Screwtape Letters is C.S. Lewis’s 1942 Christian apologetics book framed as letters from a demon.

The book consists of fictional correspondence from Screwtape, a senior demon, to his inexperienced nephew Wormwood. Screwtape offers advice on tempting a human patient, allowing Lewis to examine ordinary moral failures from an intentionally inverted perspective.

Lewis wrote the work during the Second World War. The letters first appeared in the Anglican newspaper The Guardian, and the collected book was published in 1942. Its satirical structure made abstract discussions of temptation and virtue accessible to a broad audience.

The title is often confused with Mere Christianity, another major apologetic work by Lewis. Mere Christianity developed from wartime radio talks, whereas The Screwtape Letters uses a fictional epistolary format and a demon narrator.