Which C.S. Lewis work features the senior demon Screwtape giving advice to Wormwood?

C.S. Lewis's The Screwtape Letters features the senior demon Screwtape advising Wormwood.

The book is structured as a series of letters from Screwtape, an experienced tempter, to Wormwood, his inexperienced nephew. Their correspondence discusses how to distract a human subject from faith, moral attention, and what the demons call the Enemy.

Lewis published the work in 1942. Its epistolary form lets him present temptation through reversed moral language: readers must infer the Christian ideas from advice intended to undermine them. The satire targets habits such as vanity, resentment, distraction, and self-deception.

The work is fiction, not a collection of claims that Lewis literally received demonic correspondence. The Great Divorce is another imaginative theological book, but it uses a bus journey and dialogues rather than letters from Screwtape to Wormwood.