Google Books (previously known as Google Book Search and Google Print) is a service from Google Inc. that searches the full text of books and magazines that Google has scanned, converted to text using optical character recognition, and stored in its digital database.
The service was formerly known as 'Google Print' when it was introduced at the Frankfurt Book Fair in October 2004. Google's Library Project, (also now known as 'Google Book Search'), was announced in December 2004.
Google has digitized books from libraries and publishers, and has created a searchable catalog of many more titles. Some of the books are fully searchable (those in the public domain or with publisher permission), some have "snippet view" (searchable, but not fully viewable), and some just have publication information about the book. Search results also link places where hard copies of the book may be found.
Older books that are fully searchable can often be downloaded in full in pdf, or viewed in plain text (see the upper right corner of the screen while browsing book pages).
Here is a link to the advanced search window of Google.Books: