If you loved the tense, psychological depth of 'Ripley Under Ground,' you might enjoy 'The Talented Mr. Ripley' first—it’s the obvious starting point, but the way Highsmith crafts Tom’s slippery morality is just chef’s kiss. Beyond that, 'The Secret History' by Donna Tartt scratches that itch for elite circles, moral decay, and the thrill of getting away with something. The prose is lush, and the characters are just as morally ambiguous as Tom Ripley.
For something darker, 'Perfume' by Patrick Süskind follows Grenouille, a protagonist whose obsessions make him just as unsettling as Ripley, though in a more grotesque, sensory way. And if you’re into the 'con artist with charm' vibe, 'The Good Liar' by Nicholas Searle has that same slow-burn tension where you’re never quite sure who’s playing whom.