Sentences and paragraphs are precision instruments in Rabbit, Run. Each finely honed to reflect the mood and action of the scene, and/or what’s in a character’s head. Look at the first running scene. When he starts running the sentences are short and provide small chunks of information. The first paragraph is short. Then the next paragraph is longer and the sentences get longer as Rabbit gets warmed up. The sentence length tapers of again as he’s nearing his destination, and running out of breath. The style is fluid – it moves and breathes.
When nervous or excited, Updike’s characters tend to lose commas from their speech. And when exceptionally strained or dreaming, their thoughts are narrated in run on sentences and other grammatical errors – slips that reveal their inner states. Check out when Rabbit has his hallucinations on the golf course, or the scene when Janice is going off the edge.