Characterization also plays a big role. By creating vulnerable characters, like innocent children or the mentally ill, the horror is intensified. The reader can easily empathize with them and feel their fear more acutely. In 'The Shining', the slow descent of the father into madness while his family is trapped with him in the hotel is a prime example.
Lottery horror novels often create horror by subverting expectations. You expect winning the lottery to be a good thing, but in these novels, it's the opposite. For example, the 'prize' could be something dreadful like a slow and painful death or being hunted.
Another might be 'Pet Sematary'. It plays on the fear of the unknown and the power of an ancient burial ground. The idea of things coming back not quite right is a classic horror trope that makes it a standout in this genre.
Through atmosphere. They often use dark and muted color palettes, along with eerie music and sound effects. For example, in 'Doki Doki Literature Club', the music changes to a more disturbing tone as the story gets darker.
They create horror by making the story seem real. Since it's like reading a transcript of actual footage, it blurs the line between fiction and reality. For example, in 'The Blair Witch Project' novel, the diary - like entries make you feel like you're right there with the characters in the spooky woods.
Satanic horror novels often create horror through the use of the unknown. They introduce satanic elements that are beyond human understanding, like dark rituals and unholy powers. For example, in 'Rosemary's Baby', the mystery around the satanic cult and what they plan for the baby is terrifying.
They often isolate the characters. For example, in 'The Shining', Jack is isolated in the hotel. This isolation makes the reader feel the character's vulnerability. Also, the use of psychological elements. In 'American Psycho', the main character's internal turmoil and his warped view of the world create horror. The sense of being trapped, like in 'Misery' where the writer is physically trapped by his captor, is a key factor.
They often use disturbing imagery. For example, in 'Corpse Party', the grotesque scenes of dead bodies and the dilapidated school environment immediately give a feeling of dread.
Pulp creature horror novels often create horror through the description of the grotesque appearance of the creatures. For example, in 'The Call of Cthulhu', the description of Cthulhu with its tentacles and unearthly form makes the reader feel a sense of dread. Also, the unknown nature of these creatures adds to the horror. We don't fully understand their motives or capabilities.
IT horror novels often create fear by using the unknown aspects of technology. For example, in 'It', the entity Pennywise can manipulate technology in the town, like making the sewers seem even more menacing, which scares readers as it's something that could potentially happen in real life.
The sense of helplessness is a big factor. In many SCP stories, the characters, whether they are the Foundation personnel or the victims, are often in a situation where they have very little control. Take SCP - 999, which seems harmless at first but can cause extreme emotional distress if not handled properly. And there's no easy way to completely stop it from affecting people once it starts.