I started looking for an Android reading app a long time ago, and I’ve redone my search a number of times over the years, but none come close to ALreader. https://play.google.com/store/apps/details?id=com.neverland.alreader

It’s not open source but it’s free and the amount of customization beats any other app I’ve tried. For the scrolling to work to my liking I needed to dick around in the settings a bit to get it exactly to my liking, but the fact that I needed to do so is only due to the number of options available.

There are options for network libraries, but with the size of ebooks being what they are, I’ve not messed around with this yet.

Downloading a book to an Android is easy peasy tho