Before posting my complaints and criticisms below, i should say that i did enjoy the movie a lot, and i thought Matt Damon and Franka Potente were both good in their roles.
…SPOILERS…
The great thing about the book was that you got to follow Bourne on a long and circuitous search for his identity, rather than having the whole thing thrown in your lap very early on, as the movie did.
Another difference, and one that will always give a book an advantage over a movie, is that the reader of the book gets inside Bourne’s head, and can follow his confusion and his thought processes as he tries to put the pieces together, rather than simply watching his actions as we are required to do in the movie.
In the book, IIRC (it’s been a while since i read it), Bourne kidnaps his female companion, rather than offering to pay her for driving him around. But the car WAS a mini, like in the movie.
Like some others on this thread, i had also envisioned Bourne as a slightly older man - late thirties or early forties, perhaps.
Perhaps the biggest dissappointment to me was the way they changed the whole operation that he was working on before he lost his memory. I don’t know who came up with that African guy scenario, but it was pretty lame. Part of the attraction of the book was that it was not only the American intelligence services that were after him, but also people in the criminal community attached to the assassin he had been impersonating before his amnesia. His attempts to understand who was who, and why each group wanted him dead made for some of the best reading in the book. And the ending of the book, which takes place at the Treadstone house in New York, is also great.
I was also pretty pissed off when they showed the flashback scene of his attempt to assassinate the African on the boat. The explanation they offered, in which he couldn’t pull the trigger because the man’s kids were there, is the lamest piece of crap i’ve seen for quite a while. The sort of person who blows people’s brains out for a living whether they deserve it or not isn’t going to let a few kids stop him. I think they put this scene there in an effort to convince us that he was already turning into a good guy before his amnesia, rather than just becoming a nice fellow after he lost his memory. Whatever the reason, it sucked.
And while i sort of liked the “technoporn” aspect of the film, with all the whiz-bang computers and stuff, i think i would have preferred it if they had stuck with Ludlum’s time period. His book was set in a period of telegrams and operator-assisted international telephone calls that made the suspense even greater.
On the positive side, i don’t think i’ve ever seen Paris look more impressive in a movie - at least not a recent movie.