Most of Fight Club is straight up first person. Makes sense, right? If we were getting all this from an outside perspective, we'd know that our narrator and Tyler were the same person, and where would the twisty fun be in that?
Sometimes, though, our narrator shifts into the second person, talking directly to us (or someone else, at least: "You wake up at O'Hare. You wake up at LaGuardia. You wake up at Logan" (3.4-3.6). What does this shift in perspective do?
First, it puts us, as readers, right into the story. Hey, we could be one of the nameless, faceless space monkeys in fight club or Project Mayhem. Where do we sign up?
Second, it illustrates yet again how detached our narrator is from reality. He is the one waking up at O'Hare, at LaGuardia, at Logan. Is he talking to himself in the second person? Just one of many clues that our narrator and Tyler Durden are the same person.