To me it is totally clear that ebook readers will dominate. The key technology is e-ink, which is not luminescent. I believe that luminescent displays are more difficult to read and that products like sony reader and amazon kindle will get smaller, more efficient (remember, only need power to change the page, you can power this with a handleheld generator or solar cell) and eventually replace paper altogether. Also, paper requires killing all those tree things which are so convenient for breathing...
Unfortunately, the energy needed to build & power ebook readers & to generate & distribute ebooks (incl. maintaining the necessary server farms and other ICT infrastructure) doesn't grow on trees.
To be fair, it also takes a lot of energy to cut down a tree, ship it to a paper mill, boil and smash it to pulp, mold that into paper, ship the paper to a printer, ship the printed book to you...
I don't really know which will win in energy-efficiency terms. Probably depends on the lifetime of an ebook reader before it breaks or -- far more likely -- becomes obsolete and needs to be either thrown away or kept in the back of my closet until I can bring myself to throw it away. I really wish I knew how long that was.
