Where does the author use punctuation and sentence structure effectively?

This depends on what type of sentence strikes you as special. Look through your text. I like the parallelism in this quote,

I remembered suddenly that Aspen had always been this way. He sacrificed sleep for me, he risked getting caught out after curfew for me, he scrounged together pennies for me. Aspen's generosity was harder to see because it wasn't as grand as Maxon's, but the heart behind what he gave was so much bigger.”