Are you insane or haunted?

'Things are not where you left them. You can hear but cannot see critters crawling through the house. Is that a person watching you or just an illusion?' These books blur the line between hallucination, insanity, and the supernatural. Is the narrator really reliable or denying reality? Is there a monster stalking the group, or are they all suffering from exhaustion and lack of sleep? Is it a man or something worse?