Up until just now, I mostly hadn’t read James S.A. Corey’s Expanse short fiction, because I still have this printed-book-era hangover about short fiction where I think it should be collected into a volume of short stories. But of course, in the modern world, a novella is a full-fledged reading unit all on its own; when I noticed that Amazon was selling all these things as standalone books—and that I’d just finished reading multiple novellas without thinking twice about it—I decided that it was time to go back and catch up on the Expanse stuff I’d missed along the way.
What’s fun about these is that they’re not telling stories about the core Rocinante crew, by and large—they’re about people on the edges of the story, who are involved in the stuff going on in the books, but who aren’t quite in the center of the frame in the main novel sequence. It’s a good way to add depth to the universe, to flesh it out and see what it feels like for people who aren’t interplanetary famous heroes.
So yeah, if you like The Expanse novels, you should also read the novellas. (In fact, I’d argue that they’d be best read in straight chronological publishing order, since each of these is somewhat tied to the novel that they came out near; reading them all at once is definitely not the ideal way to do it.)
The one warning I’ll give is that The Vital Abyss is told from the perspective of a sociopath, and is deeply unpleasant; it’s a good story and is illuminating an important corner of the Expanse universe, but it wasn’t nearly as fun as the rest, and was a bit of a slog to get through.