Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Dark, Objective
Although Melville occasionally seems to have a sense of humor about Captain Delano's obliviousness, the overall tone seems to be on the darker side. Think about the shaving scene, when Babo "accidentally" draws his "first blood" (75.225). Thanks, Melville, for making everyone automatically nervous at the barbershop—every smiling hairstylist now looks like Sweeny Todd.
For real, this scene is a great example of Melville's dark exploration of his characters' psyches. We've got Babo, who's found a great way to keep Benito Cereno in check, Cereno himself, who can't stop quivering like an arrow, and Delano, who doesn't have a clue what's going on.
Still, one of Melville's major strengths is staying objective. Even when the drama is high, Melville doesn't resort to sentimental monologues. Instead, he lets the characters act out their own conflicts, allowing his readers to pass the final judgment.