It makes sense to have a third tier of book: paper + digital access. I am more than willing to pay a little extra for a book if it means that I have a copy for my library shelves and I can read it on a tablet on the subway. Amazon in particular is well positioned to implement this pricing structure. Better yet, why not a subscription service? $20/mo for all the books I can read? Unfortunately, as of now, the only options for paper book fans that want to use ebooks for convenience are to pay twice, or maintain two disjoint book libraries. Like its content, ebook pricing models cling to the past.
Kane Hsieh, Why Do We Keep Making Ebooks Like Paper Books? April 5, 2013