Because A Separate Peace is a novel about reflecting on the past, its overarching tone is nostalgic and melancholy. As it sinks into Gene’s past, Knowles gradually builds tension and unease.
The novel ends back in the present with a qualified sense of relief and the release of (some of) Gene’s burdens. The entire novel is told from Gene’s first-person perspective, whether the narration is in the postwar present of the narrator or the past of his many flashbacks to adolescence. During these flashbacks Gene sometimes narrates events as they’re happening, but also spends a lot of time brooding on the consequences and causes of his actions. In these analytical, reflective passages, his tone is very earnest and serious.
In the beginning of the story Gene looks back at his time at Devon with regret, wishing he could have made different choices. He sees his adolescent prejudices and desires far more clearly in hindsight than he did originally. As the narrative shifts to his flashbacks, the tone abruptly becomes more youthful and irreverent. This lightheartedness as the narrator “becomes” his younger self brings the reader closer to Gene’s early camaraderie with his friends at school. This loving companionship is always tinged with envy, however, as Gene’s central friendship with Finny is fundamentally competitive.
As the story progresses, the tone becomes more mistrustful and tense. Gene’s jealousy of Finny grows as his understanding of the world around him—and the ravages of the war—expands. The tone also shifts as the tension between the two boys escalates. The novel feels generally darker as the flashbacks progress and the Gene-Finny rivalry grows more intense. The more Gene struggles to understand himself and questions his relationship with Finny, the darker it feels. Finny’s first accident makes this implied rift an impassable chasm. Even though Gene eventually admits he shook the branch and Finny later forgives him, their friendship is never the same as it was before Finny’s fall. Because of how central the accident is to the story, the “trial” and Finny’s eventual death all feel like consequences of Gene’s one impulsive, reckless choice.
In the final chapters, the narrating adult Gene reflects on his past mistakes and his final conversation with Finny. The tone here conveys how heavily he feels his own former inexperience and shame. Within this, however, he’s also able to find some closure, as he sees that he’s still able to grow and learn as an adult. He’s able to remind himself that—regardless of how his guilt might make him feel otherwise— his disastrous choice to disturb the branch and make Finny fall truly was an impulsive decision made in fun. The contrast between the agonized guilt of the flashbacks and the more measured present illustrates the change in Gene’s emotional perspective. It shifts from youthful catastrophism to a more adult desire to move on from the past.