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. Books are provided either by publishers and authors, through the Google Books Partner Program, or by Google's library partners, through the Library Project. Additionally, Google has partnered with a number of magazine publishers to digitize their archives.
The service was formerly known as 'Google Print' when it was introduced at the Frankfurt Book Fair in October 2004. The Google Books Library Project, which scans works in the collections library partners and adds them to the digital inventory, was announced in December 2004.
The Google Books initiative has been hailed for its potential to offer unprecedented access to what may become the largest online body of human knowledge and promoting the democratization of knowledge. But it has also been criticized for potential copyright violations, and lack of editing to correct the thousands of errors introduced into the scanned texts by the OCR process.
As of April 2013, the number of scanned books was over 30 million, but the scanning process has slowed down in USA academic libraries. Google estimated in 2010 that there were about 130 million unique books in the world, and stated that it intended to scan all of them by the end of the decade.
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: