Looking at a bunch of short novels you can finish in one sitting is actually super interesting because genre totally changes the reading experience, not just the plot. A mystery or thriller that length, something like 'The Murder of Roger Ackroyd' or a classic noir, is built for that tight timeframe. It's all forward momentum, clues parceled out with almost mathematical precision, because there's no room for a slow-burn subplot. You get that concentrated dose of puzzle-solving tension.
Romance shorts, though, operate on a different logic. The commitment is lower, so they often dive straight into the meet-cute and the central emotional conflict. The satisfaction comes from that swift, decisive arc from attraction to resolution—it’s a shot of serotonin. Literary fiction shorts, say 'The Metamorphosis', use the constraint to magnify a single, haunting idea. The brevity makes the absurdity or tragedy feel more inescapable.
Science fiction and fantasy in novella form have to be clever about world-building. They can't spend fifty pages on lore, so the best ones, like Ted Chiang’s work, embed the rules of their universe seamlessly into the action. The genre premise becomes the plot engine itself. So yeah, a 'day-length' book isn't just a short novel; it's a different beast in each section of the bookstore, tailored to what readers of that genre seek in a compact hit.