Re: Not WYSIWYG @ Primus Secundus Tertius
First: save yourself the trouble. No, the author has not "used themes and styles properly". Almost no-one does that, because it's so much easier not to. That's been a problem with Word since pretty much day 1 - I routinely deal with Word documents written by 50 different people, all software professionals - and barely 20% of those know how to use styles, or can be bothered to learn despite all the times I've tried to educate them.
Second, even if they did, what the hell is the point of changing all that at a stroke? What is the use-case where you'd want to do that? If the author is creating content for a specific audience, that has to go into a specific format, then that's what "templates" are for - give them one and let them get on with it. Anyone who's capable of using "themes" correctly is, automatically, also capable of using a template. If you really want to change all the styles later, you can write a macro for that (and store it in your own normal.dotm, so you can run it on any document you like, themed or not).
Third, what does that have to do with writing a novel anyway? Just how many subheadings and captions does the average novel include?
Personally, my text editor of choice is Notepad++. When writing a long book, I create separate files for each chapter and keep them open in different tabs. Easy enough to merge them when I'm ready.