Depends on device, but retina quality I would say. You cannot see individual dots so text appears like high quality print. The example screenshots are high resolution, you have to click them.
I think you're right about the screenshot resolution.
Something is wrong with the layout that makes it awkward for me to read. The word spacing, at least, seems awful. Look at the lines "meaning behind printed words ..." (near top) and "widely believed that ..." (near bottom) compared to the lines above and below them.
Maybe it's the full justification adjustment - the text in the box is much better. Even the dictionary popover has word spacing problems.
