
The first book ended with Isla Nublar being carpet-bombed by the (funnily non-existent) Costa Rican air force, hence InGen's new ruling bureau's (and in the second book, Biosyn's) need to go to "Site B" and get their dinosaurs there. In the novel, she's his daughter, but in the movie it's not explained or remarked upon, possibly because Gerry Harding's role in the movie is so small (it's larger in the novel) that reminding the audience of his existence would just be confusing.
Sarah Harding has the same surname as Gerry Harding, a member of the Park's staff in the first movie.Dodgson's Big Bad role is effectively taken by Ludlow ( both even die the same way). Eddie Carr and Doc Thorne are merged, as are Kelly and Arby. John Hammond (still dead in the book's continuity), Roland Tembo, Nick van Owen, Peter Ludlow, Dieter Stark, and Ajay do not appear in the novel.
Key characters from the novel like Doc Thorne, Richard Levine, Arby and Lewis Dodgson are omitted from the movie.
Adaptation Distillation: The movie keeps the novel's basic premise and some of its characters, but is otherwise very different.