Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
“The Fall of the House of Usher” tells a terrifying story, and the narrator is up front and center for the most bizarre parts. But it’s important to note that this tale is told in retrospect, so the deliberate authorial tone isn’t at all compromised by the frantic mania of a horrified narrator. For example, take a look at this second-to-last paragraph: “For a moment she remained trembling and reeling to and fro upon the threshold,—then, with a low moaning cry, fell heavily inward upon the person of her brother, and in her violent and now final death-agonies, bore him to the floor a corpse, and a victim to the terrors he had anticipated.” (41) Poe’s story unfolds in a careful and calm manner, keeping its respectful distance from the more inexpressible details (see “Point of View”) and maintaining perspective on all the crazy goings-on. In a way, this calm approach to such abnormal events is a bit horrifying in itself; the author treats the tale the same way you might disclose a trip to the grocery store.