There is an old adage in film that goes something like this: The person who knows what they're talking about leaves the theatre and says, "I loved that movie, it was nothing like the book." The obvious inverse would be, "I hated that movie, it was exactly like the book."
Books and films are two different mediums of artistic expression. One paints a picture with 
words, the other put words in your head using pictures. That is, makes you think about what the character is thinking. One old warhorse that has been trudged out endlessly is that with books you have to imagine everything and with movies it's all given to you. Well, maybe. It depends on what aspects of the work one is talking about. For instance, a book has the great advantage of telling the reader exactly what the protagonist is thinking, either through first person narrative in which we literally get a story from the unique perception of the protagonist or in another form, third-person omniscient, where we are entitled to know what everyone is thinking. When the protagonist walks up to an outwardly beautiful woman who is inwardly cold and hateful, the writer can tell us, "As he walked up to her all he could see was a miserable, wretched woman, not the beautiful face she showed the rest of the world." Translate that to film and you have to rely on the actor to provide enough subtle expression to make us understand that. To which I ask, which requires more imagination?
When most people say books require imagination what they're really saying is that the reader decides what characters and places look like. What they think is provided for you. In film, what characters and places look like is provided for you, what they think requires the mind of the viewer. I'd say that requires a little more imagination.
On the other hand, a book is not constrained by running time. As a result the author is free to explore deep feelings of characters and delve into multiple subplots. By their freedom of length books have a great advantage in providing more exposition useful to the reader in determining all the motivations and nuances of the characters. Films, constrained by length, often forfeit deeper development of character that would be useful to the viewer in understanding the character in favor of highlighting only that which is necessary to thrust the story forward. Here, literature easily wins out by allowing us a full and rich exploration of the characters.
So obviously by these two differences we can see that books and film are clearly at odds with each other as to how to tell their story. Which is why filmmakers often make decisions when adapting a film from a book that baffle the faithful reader expecting to see a page by page translation up on the screen. Sometimes it is necessary for the visual translation to work, sometimes it is an artistic decision and, yes, sometimes it's just laziness on the part of the filmmaker.
All of this leads us to Stanley Kubrick's 1980 masterpiece The Shining, adapted from a book by Stephen King. The changes Kubrick made from the book to the film were extensive. King was 
not pleased and eventually wrote a miniseries based on his own book that faithfully transposed the page to the screen. But Kubrick's is better, much better. Because Kubrick understood film was a visual medium and as such allowed possibilities that did not present themselves to the author, King, writing the book. Oddly, some of the most visually expressive moments of the book were exactly what Kubrick nixed.
Danny, has a friend, Tony. No one else can see or hear this friend. In the book he is a shadowy figure in the distance communicating with Danny. In the film, this visual motif is abandoned and Tony instead lives inside Danny's mouth. In the book, topiary animals on the grounds of the Overlook Hotel come to life in menacing, threatening ways. In the film, a hedge maze is substituted, standing still and lifeless. Or perhaps just indifferent.
There are many other minor changes but this post will deal with the big difference, that is, the ending of both stories. *1*
In the book, King makes more than a few story choices that are inconsistent logically with his characters or their situation. For starters, he gives us a grand hotel, a jewel of the west, a pride and glory to its owners. It is a palace that is to be cared for with a delicate touch. And, oh yeah, there's this decades old malfunctioning boiler that needs to be adjusted every day or the hotel will blow up. I'm sorry, what? Huh? Can the reader honestly believe that if the owners of the Waldorf Astoria were dependent upon daily adjustments to a rusty old boiler to keep their hotel from blowing up that they wouldn't just get a new boiler? To the even halfway perceptive reader this signals immediately how the story will end. So much for surprises. Wisely, Kubrick cut the boiler subplot out completely.
Then King takes the boiler subplot a step further off the precipice of disbelief. They are several ghosts at the Overlook. Since the hotel is their old haunt, so to speak, and it is in their vested interest to keep it from blowing up, they must make sure that the caretaker, Jack Torrance, adjusts it every day. Why? Because, as ghosts, they cannot do this themselves. They are non-corporeal. Except for when they move bottles and furniture around the place to signal to 
Torrance that they are there and bring inanimate topiary animals to life. But for some reason unknown to sentient beings everywhere, they just can't adjust that damn boiler. Disbelief officially unsuspended.
And finally, it seems, the whole reason Jack becomes unreliable at adjusting that boiler is because the ghosts seem to be driving him towards insanity. Hmmm. "We need him to adjust the boiler. Hey I know, let's send him off the deep end." Disbelief still unsuspended. Now I'm getting angry.
Unless you haven't been paying attention, you can see where all of this is leading: Jack goes crazy, boiler goes unadjusted, hotel blows up. About as mystical, spiritual and haunting as sticking a flashlight under your chin and shouting, "Boo!"
Now let's look at Kubrick's ending.
By dropping the boiler subplot completely we now have a hotel (and it's ghostly inhabitants) not keeping themselves from destruction but ensuring themselves new life, an important distinction. Now it would seem their slow maddening of Jack Torrance has a purpose. He is the caretaker, and the caretaker will provide fresh blood. The caretaker will give the hotel a sacrifice, his wife and child. And that will keep the hotel going.
Jack has a conversation with Delbert Grady, who has already given his wife and children, and then himself, in sacrifice to the Overlook.
Jack Torrance: You WERE the caretaker here, Mr. Grady.
Delbert Grady: No sir, YOU are the caretaker. You've always been the caretaker. I ought to know: I've always been here.
Jack doesn't understand but Grady insists: Jack was always the caretaker. As Jack falls deeper and deeper into insanity, spurred on by the ghostly Lloyd the bartender and Delbert Grady, he becomes murderous. He pursues his wife and child with the intent of killing them. Because of no boiler subplot, we are allowed to witness the devolution of Jack into a psychopath with no distractions. The ghosts are allowed to push him further, with no obvious contradictions of the Overlook's health being put into jeopardy as a result. As Jack pursues his son through that lifeless, indifferent maze his insanity begins to work against him. Danny has taken him out of the hotel that has protected him in his madness and into the environment where he must fend for himself. His confusion is apparent, the maze simply becoming the personification of it. He gets lost, and wandering aimlessly, freezes to death.
Then Kubrick takes us into the hotel. The camera begins a slow zoom into the main ballroom. As the far wall gets closer, pictures can be seen. Finally, we arrive at the center picture, a photo taken at the 1921 4th of July Ball. In the front of the crowd, with champagne glass held high, is Jack. He has always been the caretaker. And he will be again. In some other person, in some other life, he will return and give new life to the hotel. In this final moment Kubrick turns the story arc upside down and makes it clear that the Overlook, not Jack or his family, is the main character of the story. The hotel is everything, and the hotel will keep going. It will remain a vortex that draws in misery and sadness and desperation.
The ending is at once mystical, spiritual and disquieting. It was an artistic choice made by a director that gave the story and the hotel an eternal time frame.
Not every book made into a movie has such clear cut opposite choices working against each other and certainly not every movie exceeds the book. Surely, most King fans would agree that the movie versions of his works rarely hold up to the original source. And in the cases of other authors there is simply no contest. I have read the works of Twain and Poe extensively and no film version of any of their works has ever even approached the wit and poetry and artistry of their written words. Likewise, any filmmaker adapting Dickens or Shakespeare would be wise to keep the story just as it is. But sometimes a movie can make major changes to a book and come out (no pun intended) shining on the other end. This is one of those cases. Kubrick made drastic changes to the end of the story, and by doing so, drastically changed the motivations and fates of the characters. He made a movie from a book and the movie won. Handily.
Turn the page.
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*1* I think it was Neil Sarver who said he couldn't stand the "Talking Finger" choice for Danny in the film and I agree. Having Tony appear shadowy in the distance is a much better device where the book has the upper-hand. There are a few more small choices like that where I think the book is better. I also like that Tony is Danny's future, which isn't explored in the film at all.
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