My preferred method is now to cut up my books and scan them. Having a digital version (for personal use only) is far better than a print version. Of course the down side is that I must destroy the binding of every book. Once they are scanned in as pdf's, I make a table of contents and voila...I have a beautiful digital book.

That being said, if you look on the internet you can find downloadable pdf's (at no charge) of virtually any textbook you can imagine. There are of course, legal, ethical and moral implications for this, and I am in no way recommending this course of action, but merely informing you of the existence of these pdf's.