The Directory of Open Access Books (DOAB) is a discovery service for peer reviewed open access books and book publishers that indexes and provides access to high quality, open access, peer-reviewed books.
The Internet Archive hosts over 41 million books available to anyone with access to the internet. The link above will take you to a list of texts in the public domain.
More than 9,000 Open Access books from 100+ publishers, including Brill, Cornell University Press, De Gruyter, and University of California Press, are now available at no cost to libraries or users.
Choose among free epub and Kindle eBooks, download them or read them online. The collection's focus is on literature and older works for which U.S. copyright has expired.
The American Institute of Mathematics (AIM) seeks to encourage the adoption of open source and open access mathematics textbooks. This list of open textbooks meet the evaluation criteria set by the AIM editorial board.
The B.C. Open Textbook Collection is home to a growing selection of open textbooks for a variety of subjects and specialties. This is a subset of the BCampus OpenEd project listed under "Databases" in this guide.