QwertyWEB

Google Book Search searches the full text of books that Google scans, converts to text and stores in its digital database of over almost 10 million books and still expanding.
Google Book Search allows public-domain works and other out-of-copyright material to be downloaded in PDF format. Where as all the other content is only available for limited preview as per groundbreaking agreement with authors and publishers.



And now recently Google Books has started offering free downloads of books that are out of copyright and in the public domain comprising of more than one million  public domain books in an additional format, EPUB


There are still many tricks to download even books that are copywrited or banned books .

1> Google Hacks is a search helper tool that helps users to use Google Search functions. The software program that has its project homepage hosted on Google Code

Google Hacks is a compilation of carefully crafted Google searches that expose novel functionality from Google's search and map services. For example, you can use it to view a timeline of your search results, view a map, search for music, search for books, and perform many other specific kinds of searches. You can also use this program to use google as a proxy. 

It is available for windows , mac as well as linux users !
Extension are of mp3 ,wma and ogg ,
Categories :

1. music
2. book
3. video
4. tools
   
5. hacks
6. proxy
7. lyrics
8. fonts
9. application
10. torrent
11. cache
12. web hosting

Here is complete list 

2> Google Book Downloader is another great tool with  a small windows application to download any book including the limited preview books using several proxies and merge the images in a PDF file.
Google Book Downloader will only retrieve the pages that are available online, so you won’t be able to download entire books in most cases.
The application requires .NET Framework 3.5 SP1. 
GBDownloader-0.6.3.32614 is the latest version 

Google Book Downloader is a utility that rips books from Google and saves them as PDFs so you can view them with any device or desktop that can view this file format.

   Using Microsoft’s .NET framework, the Google Book Downloader application allows users to enter a book’s ISBN number or Google link to pull up the desired book and begin a download, fishing off with exporting the file to a PDF. Full setup instructions and download are available on Codeplex. 
Paste the book id of the book you want to download.
Press "Check" button. Book will be checked and all available pages will be retrieved.
Press "Download entire book" button. All available pages will be downloaded.
Press "Save entire book as…" button. All downloaded pages will be saved.
It will take a lot of time ...
 Link : http://googlebookdownloader.codeplex.com/

3> IE trick  

• Open your Internet Explorer through administrator user .Then, go to the url page in books.google.com that you want to download.
  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.
• In your Internet Explorer, refresh the page and browse the pages of the books that you want to download.
  Refresh the “Temporary Internet Files” folder. 
• Copy all PNG files to another folder. 

Since its a n image file , you can use a number of methods to convert it to PDF like Adobe Acrobat or Irfan View  (You may as well change all the PNG files required to individual JPG’s, then batch process the JPG’s to a complete PDF consisting of all the original pages from the google book. )