Just a point... I think to a certain extent we have to be careful with respect to how far we take the photograph/book analogy. I know that there will probably always be film enthusiasts amongst photographers, but I suspect that in another decade or so, those enthusiasts will represent at most a tiny fraction of those taking photographs.
In contrast, I personally expect that paper books will probably retain a significant portion of the book market. As much as most of us like to think of the content being the thing we most care about, for many the medium is as important as the content. Its why to this day that many books are sold in hard back; there are many people who simply prefer to read books that way. There will, I suspect, always be a significant fraction of the reading public who will prefer to have their house filled with books. Heck, I like the idea myself... if only I had a 6000 square foot house as opposed to the 980 I actually have
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Bill