Stephan Vandenborn’s review:
You know the haunting movies of the past decade became cookie cutter when you see this film. Because this one is the king of all haunted houses movies. And you know what it's just one room. It's just that it's hitting the sweet spot of cool sound effects, music, atmosphere, the protagonist giving you visceral feedback on the things he witnesses in that hotel room and so on.
The fact that he actually is sceptic and writes to debunk (troll) the established "hountedness" of the places that he goes to will blow up in his face with all kinds of freakish illusions, out of body experiences and ghostly indoctrination from the room that tries to slowly make him mad. It does that by playing on the sensitive things from his past.