Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Cynical
Let's face it: Turtle is cynical. She might be just an eleven-year-old kid, but she packs so much sass into her outlook on life that she comes across like a grumpy old lady much of the time. She tells us stuff like:
Kids lie. We have to or we'd never get anything. (6.1)
Or how about this:
It's a fact: if a kid is being nice, he's probably up to no good. I guarantee you some kid was behind the Titanic sinking. (14.1)
Our main girl doesn't exactly have a whole lot of faith in humanity or optimism about the way the world works, right? The thing is, for Turtle, she doesn't have much reason to think otherwise. She's had her fair share of mean pranks and lying brats in her life, so now she thinks all kids are just as bad. She also sees right through adults, and after watching her mom get her hopes crushed by men so many times, Turtle understandably isn't super impressed with the world. And since this cynical kid is our narrator, well, the tone of the book is cynical as well.