Of course, it's a King novel. The description of the Space Cowboy in the corner, and the way Jessie's never quite sure if he's there or not, is particularly terrifying. Especially if you're the type of person who is disoriented when you wake up.
The way she escapes from the cuffs at the end. She flays the skin off her hand, using her own blood to grease the cuffs enough to slide her hand free. Holy mother of God.
The long buildup to Jessie being sexually molested by her father on the day of the eclipse is horribly, horribly uncomfortable to read. Then there's the act itself, and young Jessie's dawning confusion and fear as she tries to make sense of what's happening. The whole scene, and the moment afterwards in which her father manipulates her into keeping the ordeal a secret is pure Adult Fear.
From the movie:
The whole premise of the movie: A woman handcuffed to a bed, with no way of escape and nobody to come rescue her. Utterly horrifying, and that's before the added twists that only Stephen King could have come up with:
The whole reason the character is in this mess is because she agreed to take part in a bit of foreplay with her husband that soon turned out to be some sort of twisted rape fantasy on his part. And then, just when she starts to lay into him, he drops dead of a heart attack.
Imagine finding out that your spouse, with whom you've been married for years, is secretly harboring some deeply disturbing fetishes, and that they've managed to keep it a secret from you all your life.
Then comes the dog...
The worst part about the dog is that it's ultimately just trying to survive.
And then there's the goddamn Moonlight Man. As if slowly starving to death while handcuffed to a bed in the same room as an increasingly desperate and hungry dog wasn't enough, there's apparently some sort of freakish monster hiding in the shadows. For much of the movie, it's unclear if he's the Grim Reaper, some other evil entity, or simply the result of Jessie losing her mind, which only makes his presence even more unnerving.
Only at the end of the movie do we find out what his deal is, and boy friggin' howdy, it does not disappoint. As it turns out, he's real, but he's not some supernatural monster waiting to take her soul. He's a deformed, necrophiliac, patricidal serial killer who snuck into the house while Jessie was sleeping. Lovely.
And of course, the infamous escape sequence described above is recreated in all its graphic, nauseating glory.
Just the certain facts Jessie seems to know while she and hallucination Jessie discuss the escape plan which leaves Hallucination Gerald disturbed by how she knows so much about that.