- will allow organizing the books _exactly_ was I want (why isn't by percentage read an option, or chronological by date of publication, or timeframe covered)
- allow flipping through pages of a text quickly with a re-draw/re-fresh rate which actually allows reading individual words as I turn pages quickly searching for a specific passage
- allow for a high-quality, detailed reproduction of an image, either in incredibly high resolution with subtle details (like to a printing of a b/w engraving with two black plates) or in full colour (and for extended colour range there was Hexachrome which I wish had become more popular)
- have the same contrast as a piece of paper w/ bright white paper under UV light, or even a Kelmscott Press edition (which has the blackest ink I've ever seen)
- allow _beautiful_ typesetting and will not allow widows and orphans and stacks to occur (in a re-flowable format --- no fair claiming PDFs are ebooks when folks sneer at them as not being ebooks, or presenting a collection of pixel images in a wrapper as an ebook)
Bonus points if the text is actually correct --- I've never read an ebook in which I did not report at least one typo (and that includes _Dune_ ("pogrom" was rendered as "program" and there was an error in the formatting of a glossary entry in the edition which I re-read) --- that said, the ability to directly report errors is nice, and fai r easier than tracking down the editor of a given volume at a given publisher (which reminds me, I need to check for an updated copy of _The Fall of Arthur_ by J.R.R. Tolkien to see if the typo I reported has been corrected).
The world would be a better place if authors would take typos as seriously as Donald E. Knuth does and give out reward checks (I have a physical one for $2.88 for his _Digital Typography_ --- and need to find a typo in a more recent work so as to have an account at the Bank of the Island of San Serriffe).