Not a joke; the Screwtape Letters is a seminal piece of literature, forget the written story, the story is the context of the novel, it's intention, it's composition, and it's ultimate weakness as a intellectual milepost. It practically destroys itself. It's a masterpiece of self deception.
It doesn't destroy anything lol, it's just bog-standard, annoying, heavy-handed, Western Christian cringe thinly describing itself as apologetics. It's annoying as fuck when people pretend it's literature or something.
