There are numerous differences between New Moon the book and New Moon the movie. This article covers some of the differences; many insignificant changes have been left out.
Warning: Book and Movie Spoilers Ahead
In the New Moon novel, Bella receives a camera from her father and a scrapbook from her mother for her birthday. In the book, the gifting of these items is only mentioned in passing. Bella does not include the dialogue between herself and her father before school in the New Moon narrative. However, the gifting is included in the film. The reason for this is most likely the need for visual explanations in a film, so it is easily forgiven and really is not much of a change.
In both the film and the novel, Bella Swan is dreading turning 18. To be frank, she is somewhat neurotic about it and it gets old fast. Because of her silly birthday dread, she tries to get to her birthday party late by claiming she has to watch Romeo and Juliet and it works, but it only happens in the novel. In the film, there is no mention of moving the party to a later time and the film is watched in English class, not in Bella’s house, as it is in the New Moon novel.
At Bella’s birthday party, she gets a paper cut and Jasper tries to attack her. Edward saves her, but makes matters worse by pushing her into a table, further injuring her. In the New Moon movie, Alice left the room apologizing and covering her nose soon after the incident. In the book, Esme behaves thusly. Alice stayed with Bella until Carlisle began stitching her up, at which time Alice leaves.
A memorable scene from the New Moon film for Jacob and Edward team enthusiasts is when Jacob shows up at Bella’s school to give her a dream catcher. It is a scene that foreshadows the Bella/Jacob/Edward love triangle. However, it never happens in the novel. In the novel, Bella and Jacob are not very close at the time of her birthday. Their friendship is just starting out. Later in the book, Jacob gives Bella candy hearts for Valentine’s Day, but that does not appear in the film.
In the Twilight films, including New Moon, Bella Swan appears to lack any motivation. She does no extracurricular activities and has no job that viewers know of. Yet, she goes out, goes shopping and gasses up her beast of a truck. In the book, she is not much better, though she does have a job. She starts at a sporting goods store in the summer before New Moon begins.
Jasper is in the school with Alice, Bella and Edward in the New Moon movie. In the book, he is supposed to be away at college. Alice and Edward are the only Cullens still going to Forks High School. Rosalie, Emmett and Jasper show up at Bella’s birthday party in both the book and the movie, but Rosalie only gives Bella a present in the movie.
After Edward leaves Bella in both the New Moon movie and the New Moon book, she sinks into a depression. She later hears Edward’s voice whenever she is in danger, so she begins seeking dangerous situations. In the film, there is a scene where she jumps on a motorcycle with a complete stranger. In the book, she does not approach the stranger or get on his bike, but she does hear Edward’s voice when she is near the man.
Bella decides to buy two motorcycles in both the book and the movie. She takes them to Jacob on La Push to fix them, at which time they begin to form a close bond. When the bikes are finished, they take them to ride, but Bella crashes. In the book, Jacob takes Bella to the hospital to get stitches. On the way, she tells him that he is beautiful. In the New Moon movie, she tells him he is beautiful while she is lying on the side of the road bleeding. She does not end up needing to go to the hospital.
Bella, Jacob and Mike end up at a movie together, during which, Mike gets sick. In the film, Jacob eventually freaks out on Mike, threatening him. He then says he feels sick and goes home. In the book, there are no harsh words between the two. In fact, Jacob brings Mike home himself.
Bella’s epiphany about Jake being a werewolf does not take place in his yard at La Push, as it does in the New Moon movie. In the book, Bella figures out that he is a werewolf and talks to him about it at the beach. Later, on the side of the road, the rest of the werewolves find out Bella knows and one — Paul — goes to attack her. That scene is similar to the yard scene in the film. However, Jacob is not there when Bella initially confronts the werewolves in the film and Bella is unaware that they are werewolves in the film. Furthermore, Bella does not confront them in the novel, though she planned to do so.
Harry Clearwater — Charlie Swan’s best friend — dies in the New Moon film and book. He has a heart attack while Bella is jumping off a cliff into the ocean, though the two incidents are not related. In the movie, Jacob tells her Harry is dead, after he rescues her from the water. In the book, Harry is not dead yet when Jacob saves Bella.
Alice’s background was left out of the Twilight film, but included in the book. In the New Moon novel, Alice learns more about her background and tells Bella about it. However, it is left out of the movie, probably because it was left out of the first one, so the whole story would have needed to be included.
A relatively long fight scene happens between Edward and one of the Volturi bodyguards near the end of the New Moon movie. It lends an excuse for special effects and action to the film, but it is not true to the novel. In the novel, there is no fight, though Edward despises the bodyguard. The only violence in that scene that is in both the movie and the book is Jane using her powers on Edward.
All in all, there are more differences between the two versions of New Moon than there are between the two Twilights, but not nearly as many as any of the Harry Potter installments. It could be because, despite the context of Meyers’ novels, they are really quite simplistic. None of her ideas is very complicated, so they translate easily to film. At least, that can be assumed.