Paterson is indeed brilliant. She gets that kids aren't always angelic, and that parents aren't perfect either, even when a family isn't dysfunctional. Mistakes are made. Naughty impulses are acted upon. Mistakes are made. And yet, somehow, by the end, there's real hope for healing.
Still, it's such a struggle to get there, and there is some weak characterization sometimes, and the unreliable narrator drove me nuts (is Grandma that difficult, or is Vinnie whiny, for example)... well, I just did not enjoy reading this, or feel enlightened, as I have done with other books by the author.
I am not surprised to see that the reviews are polarized. If a reader knows someone like Vinnie, or feels empathy for her, s/he'll probably like this a lot. Others will not like or respect the characters, and not like the book.
I recommend it for Paterson completists, maybe others who feel like most tween fiction is unrealistic.