Sorry about that... I was being an idiot.
Different subject entirely...
The Cleansing, in my opinion, really isn't a horror story.
It's definitely disturbing, but it isn't really 'horror'
It's shocking. It operates by shocking you with detailed descriptions of sick and depraved acts of sadism being commited against innocent people.
It works on the same level as Goatse or the many awful things found on Rotten.com. You read and you feel disgusted. You show it to someone and you watch their expression. It's designed to shock and it succeeds marvelously at that.
But I can't really call it a proper horror story.
A better name would be a 'revulsion story'. You read it and you feel repulsed, like you have just seen a aprticularly nasty traffic accident and the asphalt is stained crimson with some drunken motorist's entrails. However, the shock wears off before very long.
A horror story works a little differently, or at least I think it does.
A good horror story uses disturbing images not just to shock, but to take the mind to frightening places. Consider the following image: A group of men in hunting gear with rifles pursuing a group of small children in a dark forest on a foggy evening, the children are fighting back tears as they stumble through the dead leaves, tall grass, and twisted roots of ancient trees with branches so close together that the sky is completely obsucred. On little boy looks behind him and sees the outline of a man aiming a rifle at him.
. It's a disturbing image, but it's disturbing partly because it leaves questions unanswered in your mind. Therefore, the reader's mind is forced to fill in the blanks, and what it imagines is often far scarier than what is spelled out by the writer.
Another example is how monsters are used.
A hideous monster jumping out at you is shocking. That's 'revulsion'.
Now imagine this:
You are walking home at night. It's a cloudy night, so you can't see the moon nor the stars and the only light is coming from a street lamp.
Then you see something. It's something vaguely humanoid in shape but it's different in a way that is hard to describe. It's limbs seem twisted and too long. The way it moves is unusual and wrong somehow, like you're seeing something that has no right to be in this world. It just close enough to the light that you know it's there in the darkness. But you can't make out any details.
It seems to be moving away from you so you guess that it hasn't seen you and you take this opportunity to walk as fast as possible.
It turns toward you, it's eyes glowing an evil yellow. It lets out a god-awful scream that does not sound like the call of any animal on Earth.
You run. You run as fast as your legs will carry you. You run until your chest hurts and your legs are exhausted.
You run until you reach the safety of your home and you lock the door behind you.
You do not know what it was. You aren't even sure what it looks like apart from the eyes and the basic outline of it's figure.
The fact that you know so little about it makes you fear it all the more. Your mind is dreaming up terrible things to fill in the blanks. You have experienced terror.
Consider most of the pictures in the Creepy Images gallery. They are frightening because you don't really know the circumstances or the context of the picture. You don't know the story behind them and your mind creates one in it's absence.