As you read the opening of A Separate Peace, you will have to decide how it makes you feel, but I can certainly share with you how it makes me feel as I open the book. Of course, since I have read the entire book many times, my impressions are no longer exactly fresh.
As I read the beginning, I feel sadness and nostalgia for a time and place that is gone forever. I feel that I am at a museum, where what was real is no longer real because it has, as the expression says, been "preserved in amber." Gene uses language that suggests the museum image several times.
I can also see the foreshadowing of terrible events and the hint of wonderful events, since Gene speaks of "the fear that I lived in" (10) and the "uncontrollable joy" (10). This tells me that Gene's trip down memory lane will bring back terrible and wonderful events and feelings.
As the book opens, the weather suggests a mood of sadness and somberness, not emphasizing whatever joy Gene experienced in this place. The weather "blew wet, moody gusts all around me," Gene says (10), and later he talks about the "bare trees" and that it was "a gray and misty day (13). He mentions the fog a few sentences later and talks about being cold. When Gene talks about the tree, he says it was "not only stripped by the cold season, it seemed weary from age, enfeebled, dry" (14). Then he talks about walking through the mud and being drenched by the rain or fog. These details make me think that Gene might be like the tree, or like the weather, and that in spite of the joy he had experienced, this is not a happy place or a happy trip for him.