I agree with the other respondents about the importance of the isolation of the setting. Equally important is the supernatural activity of The Overlook. Danny has suppressed psychic abilities (the shining) that become stronger in the haunted setting. The past supernatural activity in the hotel becomes much stronger, awakened by Danny's telepathic abilities. The spirits become more active and the distant tragedies in the hotel's past begin to encroach into the present and the hotel begins to take over his father's weakened psyche. The events really begin to turn when Jack stumbles upon a party and fully stocked bar in a previously empty (and dry) ballroom. The ghost of a past caretaker begins urging Jack to kill his family. He initially resists but between his alcoholism and the hotel's hold on the darker side of his nature, he succumbs to madness. A perfect storm is created by the combination of the haunted, secluded nature of the hotel, Jack's alcoholism and barely suppressed rage, and Danny's psychic ability.

The change that takes place in Jack is the critical one. It affects both members of his family. Jack is an aspiring writer, and he believes that the setting will be ideal for him because he will have virtually nothing to do but write. There should be total peace and quiet in such an isolated setting. He finds out, however, that he can't think of anything to write about. This is not an uncommon phenomenon. Aspiring young writers who isolate themselves in cabins or attics or dismal furnished rooms often find themselves staring at empty pages. A young writer needs mental stimulation from the outside world. An older writer may be able to create in isolation because of having accumulating life experience, but a younger writer is likely to discover that there is "no gas in the tank." He may blame this on himself, feeling that he has wasted years of his life, that he has no talent, that he is a failure. And in some cases, as in "The Shining," he may take out his frustrations on others. The only problem is that he doesn't have enough life experience to draw on. Unfortunately, many aspiring young writers--like Don Birnam in Charles Jackson's excellent novel "The Lost Weekend," for example--turn to alcohol and/or drugs and destroy their lives.

I would say that King has designed The Overlook hotel to operate as the setting where some level of true nature of its characters are able to emerge.  It is in the isolated and claustrophobic conditions of The Overlook where the essence of characters are revealed.  Jack Torrence's own torment and sense of self- hate is externalized, primarily because of the isolated condition of the hotel.  King is able to use the setting as the looking glass into which characters externalize what might exist under layers of repressed and socially controlled influences.  Danny's talent of possessing "the shining" only becomes fully realized when he is confronted with the challenges of living in The Overlook.  The setting does not cause a sense of calm within the characters.  Rather, King uses it to bring out the worst elements that exist within them.  It is through the setting where one has a full view of these characters and their depraved condition.  King is able to illuminate this through the setting and the effect that its isolation has on the human being, almost to a point where one sees it as a state in which humans are shown to possess a part of their identity that exists beyond the clutches of society.  In this, the setting is vital in bringing this out to the forefront.