What was the title of C.S. Lewis's 1942 book of fictional letters from a demon to a tempter?

C.S. Lewis’s 1942 book of fictional letters from a demon to a tempter is The Screwtape Letters.

The book presents a series of letters from Screwtape, an experienced demon, to his inexperienced nephew Wormwood. Screwtape offers advice about tempting a human being, while Lewis uses the reversed viewpoint to examine pride, distraction, habit, friendship, prayer, and moral choice.

Lewis wrote the work during the Second World War, and it first appeared in serialized form in the Anglican newspaper The Guardian before being published as a book. The epistolary structure gives the satire its distinctive voice: readers are expected to infer the author’s moral perspective from the demons’ distorted reasoning.

The title is sometimes confused with Lewis’s other Christian works. Mere Christianity consists of arguments and broadcasts, while The Great Divorce is a theological fantasy narrative. The Screwtape Letters is specifically structured as correspondence between demons.