What no mention for Edgar Allen Poe?
Regarding the difference between novels and shorter works, Maugham once asked his publisher (I paraphrase), "why write a long novel when you can say the same thing in a short story or a play?"
I think the answer had to do with market. Apparently, readers, using the metaphor of vacations and travels, were more desirous of leisurely week-long voyages than a hurried weekend visits.