Which C.S. Lewis book contains the famous fictional dialogue between a senior and junior demon?

The C.S. Lewis book containing the fictional dialogue between a senior and junior demon is The Screwtape Letters.

The Screwtape Letters was published in book form in 1942. It consists of letters from Screwtape, an experienced demon, to his nephew Wormwood, who is learning how to tempt a human being. Lewis presents the correspondence as a satirical inversion of spiritual advice.

The book began as a series of pieces published in the Anglican newspaper The Guardian. Its unusual perspective lets Lewis discuss pride, distraction, social pressure, prayer, and moral weakness indirectly. The demons’ advice is meant to expose destructive habits rather than endorse them.

The work is not a conventional novel with a continuous adventure plot. It is an epistolary satire, meaning that its story is delivered through letters. Readers can also confuse it with Lewis’s apologetic books, such as Mere Christianity, but The Screwtape Letters uses fiction and demonic rhetoric to make its arguments.