I occasionally use Taio solely for reading purposes. It is a markdown editor and previewer. You add a folder containing your markdown files to the app and toun on the setting Preview by default, which turns it into a basic reader.
However as an alternative, I’ve just started using the mirror function of Notenik to generate .html versions of my notes, though I think I’m not using it to its full potential. I need to focus on this and create tweak the templates and CSS files to have a visually appealing .html files for reading. After all I’d need a basic html reader for iOS, though I’m not sure if I’d have navigation through out the collection in iOS