Which C.S. Lewis book argues for Christianity through a fictional conversation with a senior demon?

The Screwtape Letters is the C.S. Lewis book that presents Christianity through a fictional conversation with a senior demon. The book consists of letters from Screwtape, an experienced demon, to his inexperienced nephew Wormwood.

Screwtape offers advice on tempting a human being, whom the letters usually call “the Patient.” Lewis uses the inverted viewpoint to examine pride, distraction, habits, prayer, social pressure, and the ways people can avoid serious moral reflection.

The work began as a series of pieces published in the Anglican newspaper The Guardian in 1941. It was collected as a book later that year. Because the narrator is a demon, readers sometimes mistake the book for a manual of occult instruction; it is instead a satirical Christian allegory.

Lewis dedicated the book to his friend J.R.R. Tolkien, although their friendship later became strained. The unusual epistolary form and darkly comic voice helped make The Screwtape Letters one of Lewis’s most recognizable works.