Well, it's the same idea as the Mass Effect series; it's less about actually branching the story based on your choices and more about making you feel like the story is branching based on your choices. Of course the illusion gets shattered a little bit when you replay and find out that what seemed to be the dramatic consequences of your individual choice also happened to everyone else. But the first time through, before you've taken a look behind the curtain, is quite a ride.