Pretty much the entire book could count, but there are definitely some moments that stand out.
* The Five and a Half Minute Hallway gives a taste of the freakiness that is to come.
* Any scene involving people exploring the house.
** ''Especially'' Navidson's final excursion. [[spoiler:He goes in on a bike, and ends up on a steady downhill slope. After going downhill for a day, he turns around... and starts going downhill again. Every time he tries to go some other direction, he starts going downhill. It gets worse after that. Much, much worse.]]
* Johnnie and the pekinese.
* Any of Johnny's hallucinations.
* Navidson's nightmares about people stuck in limbo. There's this well, with all these people around it, too scared to jump in. Because if you've been good in life, then you get transported to heaven. But if you were a sinner, then you just [[AndIMustScream sink deeper and deeper into the darkness for all of eternity.]]
* The first time you encounter pages with seriously odd formatting.
* Johnny describing how you should not turn around. Just focus on the words.
* The image of a book tumbling off the edge of a bookshelf. It shouldn't be possible to make something that innocuous frightening.
* The scene where the house actually starts trying to kill the occupants. All this time, it had just been a static anomaly, safely locked away... then suddenly it isn't. Especially the description of how the ashy black color from inside the labyrinth creeps across the previously normal walls of the house like ink spilling across a page.
* [[spoiler: The thing that lives inside the labyrinth. Accurately described as a "minotaur".]] It is formless, shapeless, soundless, senseless and mindless. It can be anywhere, at anytime, so long as one thing is done: [[spoiler: Someone reads about the house.]] There's also something deeply unsettling about the fact that most passages about it are completely struck out in a way that allows the narrative to function just fine with or without the [[spoiler:minotaur]] actually existing.
* The part where everything the house ''doesn't'' have is described. For best results, picture it as a [[MadnessMantra rant coming from someone who has COMPLETELY lost their mind]]. Then while the format of the book changes to make it into a literal textual labyrinth, pretend that the rant is still being spoken in the background while you're reading the other scenes. Or that they keep alternating. And then... "Picture that. In your dreams." It goes on for so long, and is so utterly nonsensical and ''comprehensive'', that it has the effect of a trance.
* The word "house" itself in the black-and-white edition. In this edition there is only one understated PaintingTheMedium effect, and it's more effective than the more colourful ones sound to be. The word is always printed in grey and is randomly slightly displaced from the row of text in some direction by less than a millimetre, except when it randomly isn't. It varies page by page. Maybe that's even just a technical problem they were having with the different colour, but it works. Eventually you cringe every time you see the word. It really goes with the theme of how eldritch and uncanny the House is.
* The descriptions of the events that had Johnny's mother sent to Whalestoe are fairly disturbing. The Pelafina letters, however, are terribly spot on for mental illness.
** The secret message in one of the letters, if you decode it.
* Johnny's attack in the tattoo parlor, where he panics, seizes up and loses his ability to breathe, afterward finding ten finger marks on his throat. Scary, but only becomes real HONF when [[spoiler:you find out later in the Whalestoe letters that his mother tried to strangle him as an infant, and for whatever reason the sensation has repeated itself years later.]] Or alternatively, it can be just as creepy if [[spoiler: he'd lost it so badly that he'd literally been strangling himself with his own hands, in a re-creation of that event, without even realizing it]].
* Johnny doesn't become aware until well into the novel that he is looking more dishevelled and crazy the more he obsesses over the manuscript, neglecting himself so much that his teeth start to rot by the end of the book.
* The sections where Johnny starts analyzing ''[[FictionalDocument The Navidson Record]]'' a bit too deeply and [[spoiler:begins to believe he's being stalked by a monster "so quiet... you can only hear it as silence" and whose presence is completely undetectable until it rips your throat out.]] He then implies that [[TheFourthWallWillNotProtectYou anyone else]] who reads the book will encounter it as well. It manages to turn the image of a simple house into something truly terrifying. And then there's the [[BiggerOnTheInside infinite physically-impossible labyrinth]] inhabited by nothing but a disembodied growl.
** For some reason the [[spoiler: the black square]] was one of the scariest things about the book. That and [[spoiler:"Picture that. In your dreams."]], because it seemed like Zampano was speaking directly to the reader.
* Holloway's last recording. It's disturbing to see (or read a description of) a tape of a man who ''knows'' he's about to die, and who's trapped all alone in a cold, dark, endless labyrinth haunted by an unseen unknowable monster.
* When the characters discover that objects left behind in the labyrinth will get nibbled away by ''something'' over a period of a few days. And it's not like they neatly vanish — they get torn up and shredded, like they were savaged by some creature.
* The De La Warr account:
** We learn that the labyrinth--even its quasi-architectural physical features--predates the house, and even predates colonial settlement in the area. For all anyone can say, a hole in existence has simply ''been there'' for time immemorial and for no fathomable reason.
** Only two of the three men's bodies were recovered. What happened to the third guy?
* Navidson's third dream jarringly being replaced by Johnny's dream, told very intimately and from his own perspective, in which you genuinely get the feeling that it's happening to yourself as you read it. And you realise that you've become [[spoiler: the Minotaur]].
* Johnny's going to his workplace at a certain point and being told he hasn't showed up at work for ''three weeks'' while he honestly has ''no idea'' of that and thought he had been to work yesterday. Imagine not being able to account for your time (or actually, losing time out of your life) like that. It was already clear to the reader Johnny's state of mind was a mess by this point, but this scene really drives it home (to the reader, but it's also the first scene that Johnny himself is really confronted with his SanitySlippage).