Alright well lets start off with a classic Stephen King book, Misery.
The movie was released in theaters in 1990 and is rated R. With a good selection of actors/actresses and especially Kathy Bates who plays the crazy bitch from hell Annie Wilkes, portrayed a nice balance between the normal and the crazy through out this whole film. The adaption of the book was somewhat disappointing because they'd left out, or altered a lot of the scenes altogether, but as I think about it a little harder it really made it a tad more realistic in real life (and to spear the rating system).
**SPOILER WARNING**
I'll try to be very minimal of the exposure of both the book and the movie.
One scene that's missing was a young state trooper who went to Annie Wilkes house to investigate the missing of Paul Sheldon. Paul was inside the house in the guest bedroom and he was looking directly at him, but the trooper did not notice and kept talking to Annie who approached him. After asking a few questions about Paul to her, Annie went off to the house telling him that she'll fetch the Pepsi that Annie offered to the trooper. He accepts. Paul threw a heavy ashtray towards the window, which shattered, and got the young trooper's attention. After saying these words "Oh shit! It's him!", he got struck by a lawnmower that Annie was driving on, and she repeated to trample over him causing a bloody scene (to a point where his eyes popped out).
In the movie, she'd never killed anyone with a lawnmower, but instead killed the chief of police (in his 60s or 70s unlike the book) by a double barrel shotgun.
One scene that's altered was when Annie confronts Paul about him being able to escape the bedroom (where he went to investigate the house for food, medicine, and a knife) and as punishment, she drugged him with some sort of chemical into the blood stream. Also, she grabbed an axe and chopped off one of his feet in the process, but that's not all! Annie BURNED his flesh to doctor it, and at the end she told him, "I love you, Paul."
In the movie, she did actually drugged him, but used a block of wood to place between his feet. Annie then grabbed a sledge hammer and smashed both of his feet causing it to brake. Again, she told him that she loves him.
**SPOILER END**
Overall, the movie did pretty good at the adaption of the book. I believe if they'd actually followed the story, it would end up being rated an NC-17 or worse for intense blood.
Book: 10 out of 10
Movie: 8 out of 10