Most of my leisure reading, these days, is done on a Kindle with the type size dialled up REALLY BIG. My eyesight has gotten so I need to do that. It makes for a more kinetic experience, it feels more frenetic, faster, like you're racing through. Not a bad thing, necessarily, but it feels like there's an opportunity to actively design for this kind of experience, not just let it be an accident of the optional settings.
Something akin to Clive Thompson's thoughts on the Octavo format.
Maybe something like a Tap Essay.