I started reading on my phone, continued from the same spot on my tablet or e-reader, and all my highlights and bookmarks are available everywhere and can be exported directly to a document if you get a bit creative. And that's why I use it, plus because my physical e-reader can't handle anything else (and I definitely won't buy a new one), plus because everything else I've tried had more insurmountable drawbacks for me.

That is, we need to think more about the features of the free version so that it sells the paid one, and also decide who will pay regularly for which of our features, so that attracting people would be worth it for us.