By the film, I suppose you mean the Kevin Reynolds version released last year, starring James Caviezel, Guy Pierce, and Dagmara Dominczyk. Of course there are vast differences between the film and the book. Read the book, it's gripping: watch the film, it's great fun.
The writers of the film altered the later part of the book plot most. Dantes' revenge plans are just as convoluted and victorious, but the characters are different and some of them who were destoyed in the book, turn up at the end of the film in a glorious twist that lifts it above its previous versions.