especially after rereading the original trilogy. The fundamental difference is right there in the premise. Robert Ludlum's 'The Bourne Identity' starts with a man pulled from the sea, sure, but the amnesia isn't total; he has flashes, instincts, and his name, Jason Bourne, is the identity given to him by Treadstone as part of his deep cover. He wasn't a volunteer, but a psychologically sculpted weapon molded from a rebellious academic named David Webb. The novel is this dense, sprawling Cold War epic with convoluted layers of conspiracy, spanning months and continents. The movie streamlines it into a tight, two-hour chase thriller. Matt Damon's Bourne is a blanker slate, a victim of a secret assassin program he volunteered for, which shifts the moral ambiguity in a really interesting way.
I actually prefer the books for their sheer, messy scope. The villain, Carlos the Jackal, is this legendary international assassin Bourne is set up to kill, and their rivalry is the spine of the trilogy. The movies replaced that with the more modern, faceless conspiracy of Blackbriar and Outcome. The book Bourne is older, more physically worn, and relies more on tradecraft and manipulation than superhuman parkour, though he's still brutally capable. Francona, Marie's character, is a Canadian economist in the book, not a German nomad, and their relationship has a different, more intellectual dynamic. The movies took the core idea—a man hunting his own past—and forged a new, brilliant cinematic language for action, but they're almost a separate entity. I reread the books for the labyrinthine plot; I rewatch the films for that visceral, gritty atmosphere and the genius of Paul Greengrass's shaky-cam tension.