Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Sarcastic, Brooding, Hateful
From the very beginning, Briony speaks with hatred toward nearly everything in her path. Whether she is sarcastically questioning her father with lines like, "How do you know it won't hurt? Or did you hear it from God? You don't talk to anyone else" (2.21), or a description of the setting that involves a wind that "smacked the villagers into streamers of hair and shawls and shirttails" (2.22), her tone is one that conveys a dark unhappiness with—and dislike for—most things.
How else could we describe a narrator that interrupts meeting a handsome young man to tell us that "Skipping meals is terrifically convenient: It gives one lots of time to brood and hate oneself" (2.66)? Though Briony spends the majority of the book repeatedly describing her hatred for herself, she most certainly doesn't exclude anything else in her environment—except Eldric of course… eventually.