Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third person (Limited Omniscient)
Rainbow Rowell is so good at writing from inside Cath's head that you often forget Fangirl isn't written in first person. It isn't, though—our narrator is outside the story looking in, no matter how often we might feel like we're hanging out inside Cath's brain.
We see things from Cath's viewpoint on the regular in this book, and the dialogue and actions of other characters are as she experiences them. For example, when Rowell writes, "What's the point of having a twin sister if you won't let her look out for you? If you won't let her fight at your back?" (11.115), we have a front row seat for Cath's thoughts. It feels very much like first person, even though it isn't. How can we be sure? It's the story of Cath, not the story of me or I; we're told what Cath does by the narrator, not what the narrator herself does.