I didn't think the twist was really a "twist" though; it just was the story. This was a story about a guy who did a lot of shitty things, tried to worm his way out of responsibility through fundamentalist conversion, and found that doing that only made it worse. Booker didn't know what was going on at all until the end of the game. He was as confused as the player (more so, in my case, since I was pretty sure I knew what was up).
I felt the structure of this story was parallel to that of Spec Ops: The Line, which also makes no sense until you get to the end and find out what the player character has really been up to. And in that story, Walker also didn't know. Both of these characters were soldiers with PTSD, but their memory suppression happened via different means.