The reader is a place you spend hours in. That changes what good design means: fewer flourishes, steadier contrast and nothing that pulls your eye away from the line you are on.
Calm by default
Controls stay out of the way until you reach for them. Presence is visible but soft, and comments never cover the text.
Light and dark
The marketing site and the app share one theme, so the page you pick in the morning is the page you get at night.