Amazingly enough, you can read (at least apparently) entire books online at amazon.com, using the "Search inside this book" feature.

First let me tell you that "Search in this book" this is one of the greatest features that were introduced this year. I just love it. The idea is very simple: you have the ability to search online in the contents of a certain book on amazon.com. But not all books can be (yet) searched online. Anyway, to start the search, just go to its associated amazon.com page, and look for the "Search inside this book" green box. Fill in some keywords there, and you will get a true search results window.

But surprisingly enough, I was able to quickly "exploit" this feature and read more and more pages. I'm not at all a hacker, by the way. All I did was something very simple:
(1) search for some random keyword 
(2) go to one of the searches in the searched results page
(3) pick one of the returned framgents and select one or two words at the end of the text.
(4) Search again using these new keywords.
(5) The new search will return of course the text at the same page but the searched words that originally appear at the end appear now in the middle of the returned text. Pick up again another set of words at the end of this new text, and go to (4). Repeat as necessary... In this way, if you concatenate these text fragments you can potentially reconstruct the contents of the entire book. But that would be a terrible method to rebuild the book. First, you don't get any graphics. All you get is the book text in a pretty much raw format.

Fortunately, there is an way out - if you actually follow the link from the search results pane, you reach an scanned image of the selected page. BTW, you have to enter your credit card for authentication purposes, but you won't be charged. So, you get a few pages of your book this way. Even more, you can navigate forward and backward a few pages. But, again, you can apply the algorithm above: after getting a few pages, move forward as much as possible and then restart your search using the last words on the browsable page. And, voila, it appears that you can navigate further indefinitely!

Disclaimer: I don't advise anyone to "hack" amazon.com to download entire books in this way. It would be nice if you actually buy these books. I actually tested this method on a book that I bought a few days ago: Quantum Computation and Quantum Information. I could navigate forward using the algorithm above a few times, but I didn't really had time to check that I can see every single page in this book.

In the end, I wouldn't be surprised if amazon.com will block this feature after you read, say, max 100 pages per day per credit card info.