It's very common for film adaptations of popular books to change story beats, add or remove entire characters, and even forego entire endings for new ideas. That's the case with Doctor Sleep, which had the unenviable task of being a sequel to The Shining – which is famously despised by author Stephen King – and also faithful to a book that takes many of its story beats from moments that only happened in The Shining novel.
From that we get a final confrontation that plays out completely different, a number of characters who survived the book but died in the film, and more. These are the biggest differences we found between the Doctor Sleep novel and film.
The film version of Doctor Sleep opens with a shot of the Overlook Hotel sitting atop a snowy mountain. In the years since what happened to the Torrance family, the formerly glamourous hotel has been abandoned and fell into ruin. That's still a far cry better than the fate in the book. The Doctor Sleep novel – shockingly – is a sequel to The Shining novel and in the book the Overlook was destroyed due to Jack's negligence of the hotel's old boiler – something the film adaptation of The Shining changed.
One of the first scenes in the film finds Danny Torrance living down in Florida and having a conversation with Dick Hallorann – the one-time cook of the Overlook Hotel who also possessed the Shine and helped teach Danny a little bit about it. In the film version of The Shining, Dick returns to the Overlook to save Danny and Wendy from Jack, but only manages to catch an axe to the chest from the deranged Torrance patriarch.
In the book, Dick teaches Danny how to shove the Overlook ghosts into little mental boxes to contain them, but he does it while he's still alive because Jack doesn't manage to kill him in the novel.
Shortly after Dan and Abra meet in the film, she starts referring to him as Uncle Dan, mostly because a grown man talking to a little girl looks a little suspicious. In the book, Dan and Abra are related. Dan learns from Abra's great-grandmother that prior to Jack's time at the Overlook, one of his drunken, adulterous flings led to a pregnancy and that child grew up to be Abra's mother. In the book, Dan and Abra actually are uncle and niece.
Abra's great-grandmother Momo is only mentioned in the film when her mom says she's heading out for a visit. In the book, she factors much more into the story. Not only does she inform Dan that he is related to Abra, but after she dies of cancer Dan uses her "spoiled steam" as a weapon that ultimately helps him defeat the True Knot. He uses Momo's bad steam as a sort of poison that he tricks the Knot into inhaling, killing a majority of them.