I'm genuinely surprised by the number of people who have seen the movie (or the miniseries), but not read the book.  The best thing that could be said about the movie is that it is "closely based upon" the novel.  There are several points at which it fails, and it leaves out a huge whack of the greatness of the book.

The movie tips its hand early and loses all credence by casting noted crazyman Jack Nicholson as Jack Torrance.  It is crystal clear from the start that Jack Torrance is a man on the edge of attempting to slaughter his family with a croquet (excuse me, roque) mallet.  The Shining is the story of a man who mostly has his life together, having gathered up the scraps after a difficult time, and finally found some stable ground.  Only to see it all unravel before his family's eyes.

The book is largely told from Danny Torrance's perspective.  Danny knows that his dad has a mean temper, like the time he caught Danny spilling beer all over the shuffled papers in his office.  His dad grabbed his arm to turn him around for a spanking, and snapped the bone.  Danny remembers this moment clearly, even though it was many years ago.  He loves his dad, but he also nurtures an underlying wariness that is only heightened by his mother's increasing edginess, and his father's growing erratic behavior.

The story of Jack Torrance's hard work being undone lies at the heart of The Shining, particularly when seen through his son's eyes.  Danny blames The Overlook for Jack's failures, and the Overlook certainly contributes, what with the ghost bartender getting Jack drunk and all.  But to the adult audience, Jack's fall from sobriety is both understandable and deeply regrettable.  It's like watching someone trip and fall in slow motion, and there's nothing anyone else can do to help.

Jack's fall also manages to occupy Wendy Torrance, who loves her son, but is somehow never around to protect him from the terrors of the hotel.  Danny is left to "run and play" on his own an awful lot.  Wendy loves her son, of course, but her role in the novel is to be ineffective.  She is unable to stop the horrors, either those which drag down her husband, or those which attack her son.

Wendy is burdened with having made the choice to stay with Jack, rather than getting a divorce and taking Danny away to live with her family.  In a very real sense, fair or not, she blames herself for everything that happens to them from that point on.  

The Shining is a scary book about a hotel with ghosts and monsters, of course.  (And it's very effective on that count, don't get me wrong.)  But its staying power is thanks to the more prosaic story of a troubled family trying to hold itself together, but slowly being torn apart from the inside out.  The Shining would have been nothing but a movie of the week if it featured a happy, functional family.