In alternating chapters (written by alternating authors), Nick and Norah tell the story of meeting at a club and fumbling with whether they like each other (and whether the other person likes them). Interspersed with a good sense of alternative music and a bit of the NYC flavor, the story unfolds over a single evening.
The most fascinating part of the novel is not the alternating viewpoints in the chapters but the alternating authors. This reads very much like the old party game where someone tells a story and stops and the other person picks up. Sometimes the author leaves his/her partner in a corner and sometimes they try to spell out what is going to come next, but the next chapter always subverts the storyline to what the new author wants. So, it's very much fun to watch Rachel and David wrestle for control of their characters and quite revealing of the gendered differences in writing.
But is it good fiction? No, not really. It's not bad, but Cohn and Levithan are giants in YA and this experiment is more of a one-off for them. It probably won't win any awards, but its a pleasant diversion.