Fitting in with Google’s overarching mission “to organize the world's information and make it universally accessible and useful” (http://www.google.com/corporate/), Google Books is a large scale digitization project that includes current material that publishers have agreed to supply as well as older content held by major research libraries in the United States that has been digitized by Google. Google was sued by publishers in a high profile case. Google Book Settlement found in favor of the digitization project being legal, under the "fair use" provisions of U.S. copyright law.
A subsidiary of the Internet Archive, the goal of Open Library “is to list every book -- whether in-print or out-of-print, available at a bookstore or a library, scanned or typed in as text.” (http://openlibrary.org/help/faq). While Open Library does have access to public domain books via the Internet Archive, their primary goal is to serve as a catalog, with a secondary goal of getting the user to the text – either through scanned books or from bookstores.