I unfortunately had viewed the movie before I read the book, and as anyone who has seen the movie could guess, I couldn't rid myself of the mental image of Michael Cera as Nick (which seemed entirely off by the books description).
As most book to movie experiences go, I was stuck wondering why they left out so much in the movie. There were some amazing scenes in this book that would have translated to film beautifully! But this isn't about the movie, so I will move on.
If I had read this book in my teens, I think that it would have immediately been a favorite of mine. David Levithan and Rachel Cohn wrote in alternating chapters from Nick & Norah's perspectives, which was a new experience for me as a reader. You get a front row seat in their minds and see the different ways each of them react to the same situations. I enjoyed observing the insecurities that they were hiding from one another (often insecurities that were mutual), and how they overcome them in their journey to get to know each other.
I recommend this book to any fan of the young adult/romance/coming of age genre. Avoid this book if you are easily offended by explicit language.