[Quoth]

Very few novels are badly typeset. School books and technical books are variable. But ereaders work best for novels and collections of short stories. I've seen badly done magazines of short stories were the paper version has obviously tried to be fancier than a paperback collection and they seem to have badly converted source done for PDF to paper used for the ebook version. I keep it simple, like the most basic paperback novels, but the source is done for epub. That's then edited for the PDF to paper version simply by setting page size, headers, footers and more printed book style front matter and end matter. Maybe some styles changed. Going the other way seems to be more work and risk of stupid things in the ePub.
I've also found that epub2 from docx (saved as and never edited in LO Writer, save edits as ODT) can be like the LO Writer Screen, and uploading epub2 to Amazon gives the azw and so called enhanced KFX fine, the azw looking just like the epub2. The old Mobi produced by Amazon by that route matches old mobi I'd make myself from epub2.