This is not a hack, everything is already on our PC, no need to download a third party software to get the book.
The book is already downloaded to your PC in PNG format, you just need to locate them!
To locate the book just follow these simple steps:
1. Open your Internet Explorer (Not Firefox). Make sure that you are the admin of your computer. Then, go to the page in books.google.com that you want to download.
2. Now, go to “C:\Documents and Settings\%your admin name%\Local Settings\Temporary Internet Files\” of your computer. Delete all of the content of that folder.
3. In your Internet Explorer, refresh the page and browse-thru the pages of the books that you want to download.
4. Refresh the “Temporary Internet Files” folder. Copy all PNG files to another folder. You can distinguish PNG Files through its icon.
These files that you have just copied are, actually, the pages of the books that you have just browsed!! Magic. Isn’t it?