In twenty years, your average $50 ebook reader will have a 300 dpi full-color full-motion transflective screen, readable in sunlight or with a backlight. Most of the weight will be battery. It will have a tiny CPU and a relatively studly GPU, a small amount of permanent storage (less than a terabyte) and a short distance wireless network link, which will feed your headphones if you want sound, or connect to your phone or your house networks.
There will be a secondary screen on the back which displays the book's cover. You will have the option of changing that to anything else you want to display.
Many people will not bother to buy them, because they already carry a phone that can do all that, just with a smaller screen.
Surely there are other people who are the same way?
I would hate to do serious research in a world of ebooks – and any sufficiently serious reader becomes a researcher – but for general use, they probably are a good technology for most readers. Defenders of the paper book need to remember that mass reading of paper books is a historically recent phenomenon, for some values of "recent".
I am a voracious reader (generally 2-5 novels/equivalent per week, depending) and love ebooks. Carry 5 long novels, 3 YA series, 4 non-fiction books, my work literature, and an assortment of my favorite comfort/pickmeup novels/short stories/essays with me constantly and instantly searchable? Yes please.
Well, that and it's likely that when doing a literature review is hard and time consuming, people aren't quite as concerned about it's completeness as well it's easy and quick.
Many thousands of titles on a nice portable device I can take with me anywhere? Yes, please.
Also, while working at the client after hours, they showed me how to open the security cases so I can sample whatever audio I want on the store system - Makes the environment much nicer.
In 20 years there will be very few bookshops. There will be a few niche "artisan" booksellers, which serve only old fogeys and whatever Hipsters will be called in 20 years time.