The narrative voice is all Ellie. She is tasked with writing down everything the kids have been through in order to leave a record of their experience of the invasion. So she writes from her point of view, often about what she sees and hears and thinks, though she also discusses what others are saying and doing. No matter what she's telling us about, though, she also does so from her own perspective—and because of this, we get to know her better than any other character. We are totally Team Ellie.