Random example -- I just got a free copy of one of Brandon Sanderson's unpublished drafts,
Aether of Night. (Not being an author myself, I mostly mess around with other peoples' work.
)
No styles used anywhere, No chapter breaks or table of contents, just straight typing into Word, delivered as a DOCX.
Reduced to plain text, I was able to easily whip it into shape.
I used some regular expressions to strip out useless classes that were only setting some base CSS for paragraph elements (this is not critically important).
I took each "Chapter xxxx" and wrapped it in <h1> headers, then split along each one.
I replaced the ### scenebreaks with a slight variation on Pablo's simple scenebreak code.
Used the ToC tool to generate a ToC, added a generic cover image, and it looks fine on my ereader.
I didn't bother with making an About The Author or copyright page
, presumably you have some sort of template derived from Word for that, but anyway, see how