Q: What constraints dictate the length of works of fiction?
A: Same as any other product: money and time …
The most familiar form of fiction in the English-language publishing world, today, is a stand-alone bound book containing a novel. (Perhaps the second most familiar form is the series novel, which recycles characters of a setting from earlier works, optionally continuing to unfold a multi-book story or hitting a reset button between novels, as with some TV serials.)
A typical modern novel is in the range 85,000-140,000 words. But there’s nothing inevitable about this. The shortest work of fiction I ever wrote and sold was seven words long; the longest was 196,000 words. I’ve written plenty of short stories, in the 3000-8000 word range, novelettes (8000-18,000 words), and novellas (20,000-45,000 words). (Anything longer than a novella is a “short novel” and deeply unfashionable these days, at least in adult genre fiction, which seems to be sold by the kilogram.)
One would think that it’s so much easier to write a 5000 word short story (it can sometimes be done in a day) than a novel (it can sometimes take years) that they should be commoner. But trade fiction authors who write for a living seem to focus exclusively on novels, to the point where some of us don’t write short fiction at all. Why is this? Stay with me below the cut and I’ll try to give you a [highly subjective, personal, biased] explanation.