The Unkown vs The Known

One of the more unique aspects of Kubrick's The Shining is how everything is laid out from the start. The audience is told that the job Jack is trying to get cause a man to go insane, the audience knows that Jack is an alcoholic who hurt his son, and the audience knows everything they need to know about the shining all within the first hour of the film.
Yet with all of this out in the open, with the plot obvious, and with every reason to not care much about Jack or his family The Shining still manages to be insanely creepy.
I think conversely this fear is from what the audience doesn't know.

The Unkown has always been the source of most fears. What made the noise, who screamed, why did that vase move? Without an answer all of these can become scenarios that haunt our imaginations.

In the film the audience is only told what they need to know to understand the basic plot but not the details. In a way, the early expositing of information helps add to the creepy feeling the camera work and soundtrack slave away to create. But why was there a man dressed as a dog about to give someone else a BJ? Why was there a corpse in room 237? Why were the twins appearing only to Danny and no one else? Why is any of this happening?

The original Steven King novel has some kind of explanation for all of these things.

But had there been an explanation given in the film I don't think it would have been as scary as it is.
Horror novels rely on the unknown just as much as their film counterparts. But most authors aren't just trying to scare the reader, they also want to tell a complete story. That's what most readers are after when they read a long novel. Cheap jump scares and screaming won't work in this medium so authors have to coax the fear out of their readers.
With films jump scares and screams are abound, for most people a gory image and a screaming woman is enough to give the audience a sense of fear.

 One of the creepiest scenes for me was when Danny was playing with his trucks and a ball rolls in from out of nowhere. We don't see who rolled it or even where it came from. All we the audience know is that a ball just appeared. Most authors in a novel would tie it back to some of the spirits, perhaps the Grady sisters were trying to entice Danny towards them, in order to give the ball a reason for being there. In this movie, though there is no other purpose for the ball than to be scary.

That's what makes this film such a classic, the balance between what is known and unknown is toppled. The audience knows even less than they think by the end of the movie. The entire story is not laid out neatly for them. There's still a large debate around why Jack ended up in the picture at the end of the movie. Or why Jack froze so suddenly. Or what the Shining power Danny has actually is.
This lack of answers are primed to trigger the audiences to flight or fight responses.
The audience is forced to ask themselves the same questions they would while in the same situation, why is this happening, and how do I stop it?
Both questions the movie refuses to elaborate on.