- Creator Backlash: A relatively mild example. Lewis said in the foreword of later editions that while Screwtape was one of the easiest things he ever wrote, it was also the least enjoyable. As he put it, it caused a kind of moral cramp, forcing himself into a demonic mindset. He also resented it for not being something he felt he wasn't skilled enough to write - Screwtape's advice balanced by angelic advice from Heaven. And he was rather annoyed that his later more serious books were marketed as "By the author of The Screwtape Letters." For these reasons, he never wrote a sequel, though he did write a toast (a scathing criticism of the American educational system at the time and its resulting Tall Poppy Syndrome) in Screwtape's voice.
- Evil Is Cool: Averting this is pretty much the whole point, as C.S Lewis was aware of this trope. Not only is Screwtape himself a stuck-up member of Hell's middle management and a cranky Jerkass with no sense of humor, but he gives tips to Wormwood on how to minimize how much The Patient can enjoy sinning.
And anyway, why should the creature be happy?!
- Follow the Leader: Several Christian writers have copied Lewis's conceit of an Epistolary Novel by The Devil to deliver their own Author Tracts, with examples including Screwtape Writes Again by Walter Martin, To My Dear Slimeball by Rich Miller, and Lord Foulgrin's Letters and its sequel The Ishbane Conspiracy by Randy Alcorn. Let's just say that none of them has come anywhere close to the success of the original.
- Harsher in Hindsight: At one point Screwtape refers to atheism as their hot, new weapon in the 1950's. This takes on a disturbing Reality Subtext (and can be considered insightful, depending on your beliefs) given the increasing pushes for secularization in Western Society, Marxist regimes including North Korea's Kim Dynasty and Khmer Rouge and the New Atheism movement.