I'm going to assume you mean the cartoon-like version rather than the real-animal version which is not particularly well known.
I always think the book is better than the movie, and Animal Farmi s no exception. One reason is that I form pictures in my mind as I read, and I imagine what each of the characters must look like and where they live as they live out their stories. That's especially true in a novel in which the primary characters are animals. Seeing it come to life in a cartoonish movie was rather difficult, though I did enjoy several characterizations.
That being said, the movie follows the novel fairly closely. Rather than the animals talking, as in the book, a narrator generally tells the story in the movie. Old Major dies while giving a speech in the movie, while much time passes between his speech and his death in the novel. The windmill doesn't blow up and get built again as often in the movie, and any scenes with humans do not quite match with the text. But generally, the movie is accurate.
Two major things set the movie apart from the novel, though. The first is the obviousness of Squealer's duplicity as he persuades the animals that any changes are for their own good. His facial expressions and body language, if you will, are clearly deceitful and conniving. Those things are much more subtle in the text.
Second, the ending of the movie is a major departure from the novel. In both, the animals look through the window and see a "blending" of animals and humans--as if they had become one in the same. The movie depicts this quite well, and then it steps too far. Once the animals see this distortion of animals and humans, they stampede the farmhouse and we are to presume they retake their rightful place as owners of the land. That is a significant departure from the novel--and from history, frankly. We want them to assume power, but they don't.
The movie is fun to watch for 30 minutes; however, it is not a completely accurate depiction of Orwell's novel.
The movie followed the book fairly closely. Rather than the animals speaking, as it was in the book, a narrator told the story in the movie. Old Major died when he was giving his speech in the movie, while days pass between his speech and his death in the book. The scenes with humans didn’t generally match the text, but the movie was pretty accurate. Another big component of the book that was missing in the movie is Mollie the horse. Mollie is a big section of the book because of her love of the ribbons in her mane that represent being owned by a human. I found it quite sad that they didn’t include her in the movie. One major thing that sets the movie apart from the book is the departure of the book. In both, the animals look through the windows of the house and see a “blending” of humans and pigs, as if they had become one and the same. The movie illustrates this scene quite well but then it took a turn for the worse. Once the animals see the distortion of the pigs in the movie, they charge into the house and we are to assume the animals take over. In the book, we want them to take over, but they don’t. Additionally, towards the end of the book, Mr. Pilkington comes to Animal Farm for the big dinner feast but in the movie, only pigs came to celebrate and to learn how to take on and manage a farm as Napoleon has done.
Many things in the book stay the same but I will only point out a few of the more important scenes. The departure of Boxer is almost exactly the same in the movie and the book. Boxer is working long and hard hours as usual and he collapses. Benjamin calls out to the animals and they take him to the farmhouse. Napoleon arranges for Boxer to be taken away to a glue-maker but the animals think Boxer is going to a hospital. When the truck arrives and takes Boxer away, Benjamin sees a sign on the back of the truck with an animal skull on it and he chases the truck until he runs out of breath. Squealer says he was with Boxer at his death bed and that Boxer’s last words were “long live Napoleon!” Another section of Animal Farm that was the same was the execution of all the animals. In both, Napoleon announced that “there are traitors among us” and he asks the animals who are in contact to step forward. The animals do, and this is because they believe they will only be shamed upon. They believe they will not be killed because of the sixth amendment that states no animal shall kill any other animal. However, they are executed because Napoleon is leader and he basically does whatever he wants. So Napoleon probably thought by all means I will kill them because they are traitors! This leads me to my last similarity. The Seven Commandments, which were developed by Old Major, started to change when Napoleon took over. Four out of seven commandments were changed but the animals couldn’t be sure they were changing because they didn’t know how to read. The commandment that relates to the execution was no animal shall kill any other animal and was changed to no animal shall kill any other animal without cause. The best known amendment from Animal Farm is all animals are equal but some are more equal than others which was modified from all animals are equal.