When will the electronic book be viable?

When will the technology be evolved enough that it's worth buying and keeping? Also I don't want something that will hurt my eyes after hours of reading.|||Not for a while yet. It would involve producing a high contrast material with nanotechnology. It would require a technology to be able to produce a change in a pigment from black to clear at a minimum of 300dpi.|||I find that reading a book on the computer is a pain because it hurts your eyes. If they made a suitable background for an LCD screen that you could read without straining your eyes it should be viable. It should be easy just to buy a CD with a book on.|||It is, mostly. Paper is just the more traditional and preferred thing now.