Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Urgent; Reflective
Is it even possible for a book's tone to be both urgent and reflective? We're glad you asked, because the answer is yes. Look, there's a lot of action in this book. Every single chapter ends on some kind of cliffhanger, and Deryn and Alek are constantly trying to get away from something—or to something else—often while being shot at.
But apparently, this kind of living on the edge inspires a lot of reflection, you know, about family, friendship, the meaning of life—that sort of stuff. In short, the book is both awe-inspiring and aww-inspiring. See what we did there? We are just too clever.
For example, after loads of fighting each other and the German zeppelins, Deryn considers Alek's mental state:
Alek's sadness had been obvious from the beginning, Deryn reckoned.
She'd seen it when he'd woken her up the night of the wreck, his dark green eyes full of sorrow and fear. And yesterday when he'd told her about being an orphan—she should have known from his silences how raw the heartache was. (35.1-2)
Take a look through the book and note other points where the characters act and then think. It happens in almost every chapter—so much so, in fact, that if you can find a place where it doesn't, well, you just might want to write a paper about it.