You mention writing a novella as your use case, but I don't think that's a particularly difficult task for a typesetting engine. If you found typesetting a textbook with "rich" margins, annotations, and figures significantnly easier I would be more inclined to learn about alternatives.
With LaTeX I can transform my research papers to comply with a publisher's template in a few lines of code. Sure there are some annoyances such as compile compile bibtex compile, but the ecosystem is mature enough that most of these are well handled.