Which C.S. Lewis work is a fictional correspondence between a demon and his nephew?

The C.S. Lewis work written as fictional correspondence between a demon and his nephew is The Screwtape Letters. The book consists of letters from Screwtape, a senior demon, to Wormwood, an inexperienced tempter assigned to influence a human called “the Patient.”

Lewis uses the demonic viewpoint satirically: advice intended to corrupt the Patient exposes habits such as distraction, vanity, resentment, and self-deception. The letters are not presented as a literal handbook of Christian doctrine, but as an imaginative exploration of moral and spiritual temptation.

The work was first published in book form in 1942 after appearing in installments in the Anglican newspaper The Guardian. It became one of Lewis’s best-known Christian writings. The Great Divorce is also a religious fantasy, while Till We Have Faces is a mythological novel, but neither uses the same epistolary demon-to-demon structure.