Yes, surely there has to be an easier way to do all of this, and surely more than two of us see the problem. 

One thing that I can think of may be to potentially integrate something like the new micropub spec from the W3C into a more far-reaching solution: You might potentially take the email portion and instead of the other triggers, have Lambda create a micropub push to your site. With just a small amount of code you could add a micropub endpoint to your site and authorize Lambda to publish to it.

The potential benefit of doing this is that you could create an inexpensive service to do this for multiple platforms. I believe there are micropub plugins written for several CMSs (including notably WordPress) which then allows a broader “readership” (pun intended). If a user can send an email to a service, install a plugin and authenticate, it doesn’t get too much easier. Certainly more interesting than https://www.clippings.io/, which seems to be one of the very few apps left in this area.

As an aside, I know there’s a fairly big contingent in the IndieWeb community who are interested in static sites and Siteleaf sounds like an excellent CMS for that kind of use. 

IndieWeb also has some interesting collections of post-types, UI/UX, information, and code relating to some of these highlighting, notes/annotation types for web. There’s certainly a better bridge between books (especially ebooks) and the web:

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