Open textbooks are free, online learning materials with Creative Commons licenses. Many of the collections will have links to the same books, but each will have a particular focus, and items you can't find in other collections.
Most popular:
Other sources:
OER repositories contain more than just open textbooks. All content featured within these pages is free but usage rights vary. Materials in these repositories are released under a Creative Commons license while some are in the public domain.
Oakland Community College Library Research Guide on Open Educational Resources by OCC Librarians is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. Based on a work at https://nmc.libguides.com/oer and https://libguides.lcc.edu/oer/overview.
Guide Editor: Wendy Kamps-Tsao