The books they found were out of copyright and in the public domain, which meant they could read the full text and even download a PDF version of the book.

I'm excited to announce that starting today, Google Books will offer free downloads of these and more than one million more public domain books in an additional format, EPUB.

We'll also continue to make available these books in the popular PDF format so you can see images of the pages just as they appear in the printed book.

To get started, just find any public domain book on Google Books and click on the Download button in the toolbar.
http://booksearch.blogspot.com/2009/08/download-over-million-public-domain.html