I have run across many books where the binding has disintegrated and the paper has degraded, but never to the point where a book could not be read. Assuming the

I have run across many books where the binding has disintegrated and the paper has degraded, but never to the point where a book could not be read. Assuming the book was handled with care (so that the unbound pages are not lost), every book could be read in its entirety. I'm not saying that your scenario can't happen. I am saying that I would be surprised if all but the most carefully maintained digital library would outlive the cheapest of print books. Keep in mind that, at a bare minimum, a digital library must be backed up and transferred to new media every few years. You may get away with storing digital for a decade untended, but two decades is a bit of a stretch. Also keep in mind that even the slightest amount of bit rot can make an entire book unreadable. While this isn't really true of books stored as plain text, most modern formats seem to used some sort of compressed container (e.g. ePubs are compressed).