Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Our narrator Karana is not one for exaggeration or over-the-top language. You won't find her using big words or flowery phrases. Instead, her tone is clear and her word-choices are simple. Her speech is straightforward and to the point. Even when she is afraid or angry, Karana's voice is always steady in this novel. You can see this in the way she narrates the death of her father:
The Aleuts had dropped the bales of otter. They drew knives from their belts and as our warriors rushed upon them the two lines surged back and forth along the beach. Men fell to the sand and rose to fight again. Others fell and did not get up. My father was one of these. (4.33)
Do we get emotional crying or ranting from Karana? Not a chance. (Although we would have understood if she did get emotional. He dad just died, right?) Instead, she tells us what happened in a matter-of-fact way, using short, descriptive sentences. Since the novel is narrated by Karana when she's looking back into the past, the tone is pretty mature. We get the sense that she's grown up because of her experiences on the island.