Check affine.pro it’s really flexible. Some features might seem overkill. But I think that the flexibility might pay off in some situations (e.g. adding drawings, having character profiles in separate docs, add location maps, etc.)

It’s a local-first alternative to Notion. Just a few months ago they added export to pdf (there’s markdown too, of course) https://github.com/toeverything/AFFiNE/pull/2604

I don’t write books but I’ve helped written a couple textbooks which used LaTeX. I personally use TeXstudio, but there’s many clients out there. If you appreciate beautiful typesetting, you’ll likely enjoy TeX despite its learning curve.

I take the approach of doing content first and styling second. For content I don’t need anything more sophisticated than a plain text editor. I like it because it removes decisions that I really don’t need to be making at that point.

I handwrite all my first drafts, then type them into stimuwrite. The features are really basic but I have autism + a generally drifty mind, and stimuwrite helps me focus while editing.

I don’t write, but the Neorg project seems to be getting some attention from writers