Really interesting discussions at the Techonomy conference earlier this week regarding the 'Death of the Printed Book.'
Lots of great, deep thought reading in the above link but I think its important to consider that books have been 'digital' for a long time, they've just been distributed 'physically' so we could purchase, pick them up and read them.
The Internet and the rise of Amazon.com, Barnesandnoble.com, etc changed how we could purchase and receive them but not how we could read them (ignoring audio books).
That world has now changed. The Readers (meaning iPad, Kindle, etc) have arrived and the Readers (meaning you and me) are arriving.
Will this kill the printed book? The physical book store? What about the 'bookcase' business?
I believe the the answer is yes, but not in the foreseeable future. Why? Because you cant beat digital economics and physical book distribution is time consuming and costly. However, Not not in the near term because the publishing industry is wildly profitable and there are plenty of readers out there to support the slow, profitable decline of the printed book business.
What I see happening is that over time, more and more people (of all ages), regardless of their preference, will have exposure to eReaders and buying digital books rather than printed books but the real phenomena / tipping point will happen when school books are distributed on eReaders. Why? Because at that point, the eBook will be the primary, first reading, and ongoing experience. This is really already happening in many homes, just not at schools (yet).
Finally, it wont happen in our lifetime but devices like the iPad / Kindle will become the new book case and will be showing off what we've read on digital bookcases and social networks.