I don't think e-books will or should ever
substitute paper books; instead they
supplement the latter by offering certain advantages such as high portability and easier access.
When I was still at college I loved to hang out in the
library stocks and sometimes skim through hundreds of paper books. Now, even if these books had been offered as e-books back then, I don't think it would have had been the same rewarding experience. For instance, very often, when I checked out one book, I noticed another book that was just sitting next to it, and I discovered it later to be an even better resource than the one I was originally looking for. How would that be possible with e-books, where physical dimensions are not existant? Sure, someone like Google could come up with a nice search algorithm and present "related" books, but that you can do already today for paper books with a good library computer system. My point is that sometimes you have to see and almost feel a book to appreciate its usefulness.