What I will never understand is why this is needed at all. The books that I do find interesting I buy them. Sure, you can bypass paper by having ebooks. But is it really a replacement for a printed book? There is nothing like a printed book. No power needed, nor devices needed, you can go back to any page, any chapter instantly and if you have stomach even write on them. On the other side having the possibility to just quickly browse through a digital file to check if that title is of your interest or if it will serve you well if a technical book is invaluable. I have literally saved myself hours and money from not purchasing titles that turned out to be not of my interest. Imagine paying ridiculous amounts of money for technical books that then you find out the way a topic is approached is not really for you. Go ahead and check prices of for example Springer, Wiley, Addison Wesley books. And if out of print you pay a leg for a second hand one, effectively limiting access to knowledge only to people with big pockets.