Carefully Worded
This book is Victor's big chance to get everything out there without hiding anything that's happened (particularly when it comes to Ara T) or struggling with his stutter (you know, since he's writing instead of speaking). Because of this, the writing style is carefully worded—Victor's trying to make sure that everything is clear and readily understood.
To this end, Victor writes about events in a clear chronological way, adding plenty of details and observations. For example, when he's talking about how he sees Mrs. Worthington, he also adds that he senses she's not an entirely happy woman:
Mrs. Worthington didn't have to say much for me to tell what kind of day she was having. I had already seen her empty eyes. Her happy eyes. Her whiskey eyes. I had just seen her empty eyes. (7.10)
The writing style reflects Victor's own personality—cautious and thoughtful. That's the kind of kid he is, so it makes sense that he writes in the same exact way.
It's important to note, too, that there aren't any commas included in the text. This is because writing his story is a way for Victor to communicate without the barrier of his stutter, so he doesn't want any extra pauses in the text. He has enough of those in his life when he opens his mouth, and this is his chance to speak without them.