Which book by C.S. Lewis presents Christianity through a fictional demonic correspondent?

The Screwtape Letters presents Christian ideas through letters written by the fictional demon Screwtape. C.S. Lewis published the book in 1942, and its unusual viewpoint lets him satirize temptation, self-deception, pride, distraction, and spiritual complacency.

Screwtape writes advice to his inexperienced nephew Wormwood, who is assigned to influence a human patient. The letters reverse the usual perspective of religious instruction: readers hear demonic strategies while being expected to recognize the moral error behind them. Lewis uses irony rather than a straightforward theological lecture.

The book began as a series of pieces published in the Anglican newspaper The Guardian. Lewis later collected them in book form. He dedicated the work to his friend J.R.R. Tolkien, although Tolkien disliked the dedication because he did not enjoy the book’s subject matter. The Screwtape Letters remains one of Lewis’s most widely read works of Christian apologetics.