Google Books provides full-text access to many books in the public domain or out of copyright, and partial access to others.
When Should I Use Google Books?
If you have a partial or suspect citation that you want to identify
Google Books accepts all content and finds the best match for it
If you want quick, easy access to out-of-copyright books or serials
Google Books contains millions of works published since the invention of the printing press
If you want to search the full text of a book
Google Books allows users to search the full text of digitized books, returning either partial or "snippet" views of the content where search terms appear