Conversational and Sparse
The First Part Last is one giant conversation that Bobby has with himself, and he doesn't feel the need to pretty up his language. If a swear word is the best word for the situation, he says it, and he drops subjects and starts sentences with conjunctions whenever he pleases. And you know what? His style is still super readable. So take that, strict grammarians (oh wait… that's usually us).
But just because Bobby's style is conversational doesn't mean that it's brimming with excess language. No, instead the writing style is sparse. There are no wasted words, and when we do find descriptive language, it's kind of stunning in its poetry. For instance:
Her eyes are the clearest eyes I've ever seen.
Sometimes she looks at me like she knows me. Like she's known me forever, and everything I ever thought, too. It's scary how she looks at me.
And she's so new. Been on the planet for only a few months. I been thinking about it a whole lot lately. I feel old. (19.1-3)
The language couldn't get simpler. But the depth of emotion is profound.