A working solution for me was to deploy a little website to organize both my physical and ebooks in the same place. For physical books, it tells me where they should be. For ebooks, I can download the file, the website is light enough that it works fine with my ebook reader.

Surely there are bugs, but here it is, if you'd like to give it a spin: https://github.com/seanboyce/ubiblio

Interestingly enough, I had tried to find a way to add an 'email to my device' option, but it was too fiddly. I got it working with OAUTH + gmail, but setting it up was not exactly user-friendly. The simple download option worked much better.

Anyway just a weekend project I extended a little. Don't expect much polish :D