Feels like a lazy adaptation to film. Much of the movie consists of small, fractured sections taken from the book that are lacking greater context.
Also not sure if I like Jack Nicholson for this. Jack is given zero development going into the Overlook, and once he arrives, his descent into madness is near instant. I think much of his performance after the fact attempts to provide exposition and to establish motive to make up for his shoddy character development.