The book was alright, I didn't really understand some parts. I mean in defiantly did have way more details than the movie did, but I didn't really like all of those unnecessary details. But if you are a person who likes details, than i recommend reading the book.
I really like the movie, it had so much more action, and i really understood it. I am a more seeing kind of person, i need visual picture. The book was more like cujo the dog, it had more details about the dog than the book did for sure.
The difference about the movie and the book is, the book had a lot of other stuff happening in it, while the movie was just about the dog. I'm not really sure why the book had other parts that the movie didn't even talk or have anything about. So therefore the movie was better!
If I were you i would watch the movie, why you ask? Because the book was not that good, it wasn't as interesting and it doesn't catch your eye until some parts. The movie catches your eye at the very beginning, and if you're a person who likes suspense in the beginning and throughout than the movie is going to be good for you.