My absolute top-tier pick for anyone wanting genuine dread isn't a modern novel, it's an older collection: 'The King in Yellow' by Robert W. Chambers. That first half, with the fictional play that drives people mad? It’s not jump-scares; it’s this profound cosmic unease, the horror of an idea itself being a contagion. Modern authors are still riffing on it.
For a newer voice, T. Kingfisher’s 'The Twisted Ones' genuinely got under my skin. The protagonist finds her late grandfather’s weird journal entries, and the monsters are described in such a viscerally wrong way—all angles and stillness where there shouldn't be stillness. It reads like a folk horror story until the unnatural geometry of the thing just invades the reality of the woods. It builds that unsettling wrongness so slowly you barely notice you’re holding your breath until the final third.
I’d put Adam Nevill’s 'The Ritual' in there too, especially the first half in the Swedish forest. The sense of being watched, hunted by something ancient and utterly indifferent to your suffering, is a classic supernatural thriller engine, but he executes it with a rawness that feels almost documentary. The latter half gets weirder, but that initial descent is masterfully claustrophobic.