It's claustrophobic, fast-paced, disorienting, but the mcguffin turns out to be technological, which makes it a thriller rather than proper horror, though certainly the first half of the book has a haunted-house-in-space feel and the protagonist's propensity for seeing things that are probably ghosts of some sort, which ironically leaves her better equipped to deal with things when everyine else is being driven mad by visions, must be supernatural. Anyway, that's not a complaint, just an observation, it's plenty creepy and gothic.