There are many differences and summaries between the book and the movie the coronals of Narnia the lion, witch and wardrobe. For example; “In the movie, they crossed that river (jumping over ice bergs, Megrim confronting them on the river, etc), while I'm pretty sure that in the book they didn't cross it, but walked along it or something... can't fully recall. Also, I'm pretty sure in the book they were only confronted by Megrims once after Edmund betrayed them (when Peter fought him), but in the movie there was also the aforementioned confrontation on the river.
The Professor is portrayed differently - at least at the start of the book/film. He's not quite as reclusive in the book.
They end up going into the wardrobe different. In the film, they're running from the housekeeper after hitting the ball. In the book, they're trying to avoid a house tour.
The book also skips over a lot of the set-up to do with wartime and the relationship between Edmund and the others. Lucy goes to Narnia in about page 6 rather than 30 minutes into the film
In the book, while with the Beavers, once they realize Edmund is gone, they know they've been betrayed and they leave. In the film, they climb a ridge and watch him go into the palace before realizing for sure.
The book makes much more of the fact that Edmund is enchanted by the Turkish delight so that it's not all his fault. When he betrays them, he does it when he first gets to the Palace; not in the dribs and drabs throughout the film which makes it seem like he's not