Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Somber; Reflective
In "Death in the Woods," the narrator is looking back at an important childhood event that shaped the man he has become.
Because of this, the narrator spends a lot of time reflecting on the nature of the events he witnessed. He wonders "how [he] knows all this" (1.13). He adds insights learned later in life and explains how they impact his view of the story. As a whole, the narrator is looking at his memories as puzzle pieces that he desperately needs to put together. Jeez, what's the rush dude?
Given the nature of the event (the whole death in the woods part) the narrator is pretty somber too. He's clearly been affected by the circumstances surrounding Mrs. Grimes' death and feels a great deal of sympathy for her. You can see that when he describes her body as "so white and lovely, so like marble" (4.13). All of these factors combine to create a story that's both dark and sympathetic, one that both looks back to the past and forward to the future.