One of the difficulties of a screen is that you can't control how far away the reader is from the screen. With a book and mobile device the user can easily adjust distance to match their preference—on a screen you can make the type responsive to screen size, but if someone is closer to the screen or further away there isn't much that I know of that can help get this dialed.
With Xbox One having an always on camera facing you this might actually be possible, although I think that the right size probably depends on your eyes and vary depending on how far or near sighted you are—that's just a guess.
Isn't this why browsers have text zoom? On Firefox if I want to make text larger I can simply do cmd + or ctrl +. Assuming the site is coded well, the text will flow accordingly.
My pet peeve on layout is when a page is multi-column, but each column is
taller than the viewing window, so the reader must scroll or page down in
each column, then go up for the next column, then down to the next page.
This issue often shows up in PDF versions of scientific journal papers.
Bonus points if a "page down" function operates on the source page
images rather than on the window view (iow, if repeated "page down"
only shows the top of each source page, rather than each visible
part of the viewing window.) Mouse-wheel scrolling helps, modulo
interface "features".
