Well now, this makes me realize who the first real market for e-books is going to be: those who need large print. Former bookstore clerk here.
Some need large print on the page to be able to read it do due limitations on their vision. So certain popular books are reprinted in large print editions. Of course, the selection is limited.
Also, to prevent the alternate editions from having to be unmarketably large, they are very often abridged.
An e-reader that had UI to resize the text would catch on with some of the elderly…
Don’t you read other types of printed material? Dictionaries, phone books, encyclopedias, magazines, cookbooks, academic/professional journals, old textbooks, etc… I think even you would benefit from having all those on a single book-sized device.