Good hyphenation and TeX-like paragraph-level justification (tries to balance whitespace throughout a paragraph rather than just filling each line up with as mu

Good hyphenation and TeX-like paragraph-level justification (tries to balance whitespace throughout a paragraph rather than just filling each line up with as much as possible and breaking when a word overflows) would do a lot to fix that. The lack of these is most noticeable when text is in narrower columns. But even with larger e-readers it is, IMO, responsible for a lot of the “this still feels less readable than a book for some reason” vibe that ebooks (and lots of self-published paper books) still have. I really lament that in the switch to electronic text we seem to have forgotten what were thought of as basic requirements for readability in paper-based publication.