If you want something that twists the knife slowly and gets under your skin, give Alex Michaelides a shot. 'The Silent Patient' got a ton of hype, and yeah, it's a page-turner with a great premise, but for me, 'The Maidens' was even creepier. It's set at Cambridge and has this cult-like secret society vibe that's more atmospheric and unsettling. The psychological tension isn't about sudden jumps; it's in the academic arrogance and the way the protagonist, a group therapist, gets obsessed.
Otherwise, I keep going back to Tana French's 'The Witch Elm'. It's less a traditional thriller and more a deep-dive into memory, privilege, and identity after a traumatic head injury. The suspense comes from the narrator's own unreliable perspective, which makes you question everything alongside him. It's a slower, heavier book, but the payoff messed with my head for days.