Straightforward, Detailed Stream of Consciousness
Stream of consciousness is a writing style that allows us to hear a narrator's inner thoughts as they happen—and while this sometimes leads to a frenzied, incoherent reading experience, Cassia is thoughtful and careful in her narration. She shares literally every single thought and action that occurs over the course of the novel, so as readers, we have no doubt that we don't miss out on a single moment between her Matching ceremony and her scrawling I love you in the dirt of the Western Province.
The narration is so detailed, in fact, that it often defies logic. Check this out:
I sense, more than see, his hand move slightly and then drop back down. (19.18)
Is Ky's slight hand movement going to wind up being relevant to anything? Nope, of course not—but we get to hear about it anyway. This detailed style complements the curious tone pretty perfectly. As Cassia's eyes open to the world, it makes sense that she'd pick up on tiny details and wonder at their significance.