Any options for (organized) two-way ebook sync between Android and laptop?

[suenteus]

Hey all,
I'm a reader with a large library of research documents (mixture of pdfs and ebooks) that I do extensive annotations on. I'm using an Onyx Boox Note for annotating (annotations are stored inside the pdfs) - the Onyx runs Android and has access to the google play store. Locally on my laptop I'm running Calibre to organize my library, keep metadata, and just generally be able to find the docs I'm looking for.

Now what I'm looking for is a way of 2-way syncing these documents (so my annotations on the Android device are synced with my laptop) ... but also some kind of library organization system that makes it possible to make sense of 100+ books. Does anyone have any suggestions?

I can describe the setup I'm using now...

* Calibre on my laptop, which handles the task of organization beautifully
* the Calibre library itself with all the docs in it is stored on Google Drive, so is "in the cloud", so to speak
* on my Android device I use an app called "Folder Sync" that does two-way synchronizing of my Calibre library from Google Drive to my device

Now the problems with this setup...
* (the big problem) there is no library organization on my Android device... which can be a nightmare when I need to browse my books. Even though the books are stored in Calibre library format, I have not been able to find an app that will read a calibre library stored LOCALLY on the mobile device.. :-(

* (the smaller problem) synchronization with Folder Sync is a slow and tedius process, usually taking over a half hour (crazy considering my library rarely changes, except for one or two books with new annotations), and sometimes has errors - but at least it usually manages to sync my annotations so that I can later see them on my laptop

Does anyone have any thoughts/ideas on how to find a better way of working? Apps like Calibre Companion provide the library organization I need... but the sync system in Calibre only goes one way (from Calibre to the device) and it's impossible to sync in the other direction! :-/

thanks for any help or ideas!
xxsue