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Robert Ludlum's The Bourne Conspiracy doesn't follow the book, though as hard as it tries to escape any relationship to the movies, it has a really hard time breaking free. While much of this can be attributed to the game using the movie's signature quick cuts and shaky camera, the cutscenes come incredibly close to matching the movie shot-for-shot. I didn't mind it and actually thought it helped make a better game. However, I wasn't as pleased with the way the story is handled.
Although the name might lead you to believe otherwise, The Bourne Conspiracy centers on the events of The Bourne Identity, which are used as more of a loose framework. Most of the missions are flashbacks to Bourne's earlier missions, including the one that leads right into The Bourne Identity. For example, Bourne's brawl with two police guards early in the game triggers a memory of a mission in Switzerland. It's a pretty cool use of the license and really works with the story's theme of someone searching for his identity, though it also leads to an incredibly disjoined narrative. The threads that bind the flashbacks and the story are pretty thin and sometimes have little to do with the event that triggered the memory in the first place.
For the most part, The Bourne Conspiracy is a third-person shooter, though it attempts to mix in a little stealth, adding a bit of a Syphon Filter-like feel. Stealth elements are most apparent during earlier missions while later ones seem to focus more on gunplay and hand-to-hand combat.
Part of what makes Bourne a cool character is his natural instinct, which shows up in the game as "Bourne Instinct". This is basically a sort of "Spider-sense" that acts as an in-game radar; it points out important mission goals and highlights enemy locations. If you think about it, the ability is kind of goofy, but it works incredibly well as a gameplay mechanic and is enough of a breakaway from "reality" that it works within the game's context.
Another cool part is the hand-to-hand combat mechanic. The system is incredibly simple on the surface and features two buttons (X) and (Y) which perform light and heavy attacks respectively. The trick to the system is chaining the right combinations of attacks in order to do enough damage to an opponent and build up enough power for a "Takedown" move, which I'll get to shortly. Although the system features a fair number of combos, you'll eventually figure out one or two that work and stick to those. Still, the system is fun, though only when it isn't forced on you.
It's easy to incorporate the "Instinct" mechanic as a part of the natural game logic, but melee fights are inserted into areas where they go against logic. If an enemy has a gun and a clear shot, he's probably going to take that over hand-to-hand combat, especially if the other guy can kill you with his pinky. It makes sense for Bourne to do it, especially when the other guy is an innocent police officer, but not the other way around.