Cause all writers read, innit.
What feels worse in stories? Things that have happened, or really could happen in real life, as in a parent's worst nightmare for instance. Jeopardy or loss. A direct threat to your safety or that of a loved one. 'Sophie's Choice' terrified me completely, and haunted me afterwards, working out what I might have done in her situation.
Things that will almost certainly never happen, but you might just experience in some way or another, and not be sure how to respond to; things to do with the Dark; things beyond our ken? Or are they actually just weird, or basically OK, so long as they're not out to harm you, or haven't the power to do so?
Is it fear of the unknown, fear of loss, fear of death?
Last time I saw 'The Exorcist', years ago on the box, it wasn't the demon who bothered me. It was just foul mouthed and ugly and could do levitation. It was a bit gross but almost funny. I knew the little girl would come out OK, but I was worried about the Exorcist himself. He was obviously in ill health, and the previous time he'd encountered Pazuzu, in the desert, he'd been young and strong.
'Silent Hill' was far worse, truly terrible. But film has a huge advantage in the scare stakes; visually and sound track.
What frightens you in fiction, which has to set about the job without those tools?
'The Fist of God' frightened me, by Frederick Forsyth. It was about the Supergun. Worry for the two Iraqi brothers particularly frightened me, after their father was murdered. I was rooting for them to make it and.....
'Jaws' by Peter Benchley. I did not want the lovely MC to get ate. I didn't want anyone to get ate, but specially not him.
Whereas Stephen King's books might frighten me to a point, then I find it goes too far, and I'm not frightened any more. 'Carrie' frightened me, because of the young girl's unhappiness, and we all know what a zoo school can be. And 'Cujo', where an innocent animal became a thing of terror due to his rabies, and trapped a mother and son in their car and it was him or them.
But what frightens you in fiction, which sets about the job without those tools?
Titles? Characters? Lines?