The Monk

This book is BONKERS. A haughty, vain, charismatic asshole falls into evil after evil after evil, finding a way to excuse himself every time. Again and again Ambrosio freaks out over the thought of doing something terrible, and inevitably he ends up doing it and explaining it away as something God will forgive him for later. There are cruel nuns, a few ghosts, and an actual physical Satan. And way too much horrifying detail about rape. It seems insane that this was published in the 18th century.