Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Bleak as Night
Considering that almost all of the characters in The Raven Boys die or are threatened by death, it makes sense that the overall tone would be just a little bit bleak. The book doesn't shy away from describing every character's personal struggles or letting the reader see all the hard and ugly truths of life.
For example, the reader doesn't just see the shiny, rich, and charming version of Gansey—instead, we get to delve into his inner struggles. Gansey may seem bright and careless, but inside, he deeply wants to do the right thing. When he bribes Aglionby to keep Ronan around, he feels awful about it:
The conversation with Pinter gnawed at Gansey. Bribery. So that's what it had come to. He thought this feeling inside of him was shame. No matter how hard he tried, he kept becoming a Gansey. (33.3)
The same goes for the book's treatment of Blue's issues with her fate, Adam's painful relationship with his father, Ronan's hatred of his own brother, and Noah's sad recollections of his betrayal and death. Nothing is spared, even if it's not very pretty.