Mandi Rose Having read the Shining, I can't imagine reading Doctor Sleep without prior knowledge of the main protagonist, Danny. That said, I feel as though in the beginning of the book, you do get enough insight of what you would have missed in the first book. But to really understand Danny, I feel you would have to know what exactly he went through at the Overlook Hotel the way Stephen King wrote it- not the movies adaptation of what it was like. Finally, I don't believe it was terribly scary, not the way Pet Semetary is (to me at least). It is suspenseful though, I found difficult to put down. Hope this helps!
Aida The Shining describes in detail the father's alcoholism and how he was affected by the Overlook Hotel's possessiveness. It also describes Danny's special talents, such that by reading it first, you may better understand how his past experiences are motivating him/his behavior in the book Dr. Sleep.
Tressa You could read it without reading The Shining first, but you will lose out on a lot of the horror and heart of Danny Torrance's background story. I just don't think Doctor Sleep would have the same heart-wrenching effect on non-Shining readers.