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.
