I'm going to take a shot on a writing and publishing plan that takes advantage of the data recently released about how readers read, consume, and abandon novel-length (40K+ words) books.
First: About 50% of readers abandon books within 100 pages, usually due to boredom. A manuscript usually goes 400 words per page. 100 pages is 40K words. Formatting, etc. will skew that page count (and that's before adding Foreward, Afterward, Appendices, etc.) but it's fair to say that most readers now aren't big on fat books unless they're competently written OR they have external pressure to complete and comprehend the contents.
So, since publishing now (much as the Big 5 refuse to believe it) is an electronic-first affair, there is no excuse for fat books. Stuff that formerly would be an appendix, etc., should be shunted to a Wiki article instead. Manuscripts should be culled accordingly. Lots of fat needs to get trimmed out, and writers need to get straight to the point. Hit hard, hit fast, hit relentlessly, blow their minds, and move on.
Shorter books is how you adapt. No need for all this dross; throw that shit up on your author website or blog. This publishing paradigm doesn't reward flabby, undisciplined writing and publishing practices anymore. The Big 5 and their Fat Book paradigm relied on a realspace retail sales business model, and fat books consume shelfspace that otherwise would go to other books. Electronic publishing makes that irrelevant.
It also means that readers need to stop being lazy shitfucks and presume that the book has it all. It doesn't. You want answers? Go to the site and read the stuff that got cut because it's irrelevant to the book's narrative, but is part of the mound of worldbuilding (or its non-fiction equivalent) necessary to produce it. Like Wookiepedia (Star Wars) or Encylopedia of Arda (Middle-Earth).
The result is to aim for a 40-50K final draft, for a page count of about 100-120 pages, and all the addons stuff that pad the page count cut from the book for reuse as online articles. Hit it and quit, straight with no chaser.
Second: Readers want to engage direct with authors that they enjoy. This means having a website that is more than just a blog, or a landing page, and that means having regular content updates that keep your audience engaged and acts as a form of marketing because of that. While my writing blog can fulfill this function, I don't think that will do in the long run.
As I see it, having watched and read plenty of perspectives on the matter, this place needs to be where your readers go between book buys to stay engaged with you. That's why I say that using it as repository for material like Appendices is a good one. How the Empire works? Website content. Artwork of your Protagonist? Website content. Curation of fan sites? Website content. You get the idea.
Exactly what I intend to do I don't know yet. I'll let your know when I have a plan, as all I know now is that it needs to be done and I have to consider what options I have given the lack of resources I've got to work with.