I'm a daily user on an android phone, as it's the only FOSS eBook reader still being maintained that has a feature set that includes white text on black background. It's pretty good, though it has some bugs, every so often an update breaks things and a new update fixing them is released soon, so I avoid updating if my version works fine for me. And since it's aimed at e ink readers it's UI is a little clunky for a regular mobile device. Great reader, renders everything you can think of, although every now and then with specific books it can get a little buggy. I haven't looked into the bugs to file reports.