But ... what exactly does it solve? Fundamentally all it provides is a way to mechanically flip through the pages of a digital book. It doesn't replicate a real paper book, in terms of feel, smell, or nostalgia.
Ignoring nostalgia, is the ability to mechanically flip through a book important? Is that the ideal way to traverse a large volume of text? I doubt it. It's unlikely that, when humanity designed paper books they stumbled on the ideal way to handle a large volume of text.
When I'm reading things on my computer, whether they're articles or books, I never really think "man I wish I could flip through this text like a book." PgDn handles that just fine.
What I usually long for is a more portable form factor, which tablets solve, and more space. Side-by-side pages is great, not just for reading, but also for looking at different sections of the book at the same time. Again, a tablet _could_ solve that. If they made e-ink tablets larger ...
Heavy readers and researchers I'm sure will argue about bookmarking and notes. That's not unique to physical volumes; tablets can handle that. And again, probably better. Maybe we don't have the right UIs for them yet. But I guarantee we eventually will.
Basically, I don't think having a bunch of e-ink pages is what we need. We just need the readers to be bigger, faster response time, color, physically flexible, and have better UIs.
Of course, none of that addresses the nostalgia factor. But I don't think people are going to have such a strong desire for old fashioned books once we have e-ink readers that are fundamentally easier to use than physical books.
Nostalgia is always a shrinking market. Imagine someone who really wanted to access Google using the Dewey Decimal System. At least the amount of content in books remains about the same as it always has.
Jumping into almost SF realm I'd say what we need is a 400 pages A5/A4/A3 standard book. With blank pages. Those pages are made from a material that feels like paper so the book folds, is lightweight and can be flipped through. There's a switch (or a knob or whatever) on the back cover and when pressed the back cover screen allows you to select which books you want to load. Then e-superink © displays the content on all the page at once. And now you have the exact same experience you have with real books (flipping through, knowing more or less « where » you are in the story). Except the back cover can launch a search bar. Oh, and you can write on pages and it's recorded in the software which displays it again when rendering pages.
Back to reality and to some of the geek things of the early 2000's: IBM had some kind of foldable screens in the demo department. I remember some video or concepts and you could see a guy reading his newspaper on his folded screen. Attach 8 of them together in a binder and you got some kind of physical computer interface that you can easily skim, read and pass around.
edit: Dug out a 2000 wired article about that very subject https://www.wired.com/2000/08/epapers/
edit flexible screen picture: http://a57.foxnews.com/global.fncstatic.com/static/managed/i... and http://www.computerworld.com/article/2507175/emerging-techno...