Project Gutenburg is a library of over 60,000 free e-books with a focus on older works for which U.S. copyright has expired.
Directory of Open Access Books focuses on academic titles and includes 27,588 academic peer-reviewed books from 377 publishers.
Open Book Publishers publishes open access academic research in the humanities and social sciences. All books include a free online edition that can be read via the website, downloaded, reused or embedded.
Digital Public Library of America connects people to the riches held within America’s libraries, archives, museums and other cultural heritage institutions. All of the materials found through DPLA — photographs, books, maps, news footage, oral histories, personal letters, museum objects, artwork, government documents and so much more — are free and immediately available in digital format.
