Yeah, I used Google Books for work a while ago, to read a math book I didn't want to buy (because it cost over 100 dollars). They didn't let you read all of the book at once, but it was easy to get around that--I just deleted my cookies. OTOH, it seems to be impossible to print out or download the text from the site. I don't like reading long pieces of text on the screen, so I don't use the site much. But the upside is that the text is searchable, so if I want to find a book that includes, for example, "subelliptic functions" and "boundary Harnack inequality", I can.