You know, I always come back to the difference between a haunted house book and a genuine gothic. The atmosphere isn't just spooky wallpaper, it's the texture of dread. It's about oppressive, almost sentient architecture—mansions with secret passages that feel like they're breathing, ruins that are actively crumbling under the weight of their own past. The environment isn't a backdrop; it's a character, and it's always sick or decaying. A pervasive melancholy clings to everything, a sense that time has gone sour.
What really sells it for me is the psychological claustrophobia. The protagonist is often trapped, physically or socially, in these decaying spaces, and their perception starts to warp. Is that a ghost, or is it their own unraveling mind? That ambiguity is key. The supernatural might be real, or it might just be the fever dream of a character being crushed by inherited curses, forbidden knowledge, or monstrous secrets festering in the family crypt. I'm thinking of books like 'The Haunting of Hill House' where the house itself is the monster, or 'Wuthering Heights' with its storm-battered moors mirroring the characters' violent emotions.
It's that delicious, slow-creep unease, where the setting and the psyche become one rotten thing.