ePub to PDF, passing through TeX
@roger64: 1) Neither am I a professional when it comes to publishing (but I do have a fairly wide background in computing): I'm but learning step by step, from resources on the Web. 2) Then you might try writer2latex or writer4latex someday (never did, I don't have LaTeX installed). No Libertine though without XeTeX. There's a "legacy" package that can use Biolinum. And a TexGyre Termes font built from a Times New Roman clone (because of licensing issues). But there's a bunch of pretty good fonts available, see the "Latex Font Catalog" website.
@Jellby: True. But with some restrictions, on CSS mostly, it becomes fairly easier. And you get a typesetting engine, that is printing quality, where Prince, as far as I can see, doesn't give you much more than "export as PDF" in Word or OO. It all depends on what you're doing PDF for.