Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Uptight and British
This is one uptight narrator. Arthur can't even say that bad weather makes him depressed without mincing around, we suspect with his nose in the air:
My spirits have for many years now been excessively affected by the ways of the weather, and I confess that, had it not been for the air of cheerfulness and bustle that prevailed in the rest of the house, I should have been quite cast down in gloom and lethargy (1.4)
Throughout the whole book, Arthur talks in his very British way about everything, avoiding the fact that he's going through some really rough stuff. There are no expletives, no choppy sentences, no exclamations of despair—just stiff upper lip, even when he's facing down a ghost.
We can also see this in the way that he handles his new family when they bring up ghost stories: he deflects like a pro. Instead of explaining to them his horrid past, he excuses himself and goes for a walk. Just like a man. A British man.