Which C.S. Lewis book records conversations between a senior demon and his nephew Wormwood?

The Screwtape Letters records conversations between a senior demon and his nephew Wormwood through a series of letters.

C.S. Lewis's book was first published in book form in 1942 after appearing in the Anglican newspaper The Guardian. The fictional letters are written by Screwtape, an experienced tempter in Hell, to Wormwood, who is assigned to influence a human “Patient.”

Lewis uses this reversed perspective to satirize temptation, self-deception, bureaucracy, pride, and shallow religious habits. The humor comes from allowing demons to describe destructive behavior as professional success, while the reader recognizes the moral danger beneath their language.

The book is an epistolary work, meaning it is constructed from letters. It is not a diary, although its imagined private correspondence can lead to that mistaken description. Lewis later added a short piece titled “Screwtape Proposes a Toast,” first published in 1959, but that is an appendix-like sequel rather than part of the original 1942 sequence.