If you are interested in using an Open textbook or other OER materials, please talk to your subject librarian or email Mahrya Burnett, Scholarly Communications Librarian for help on getting started. In the meantime, check out the Open Education Resources online subject guide: https://guides.lib.uiowa.edu/oer/home.
There are many definitions of OER, but the University of Iowa has adopted the following, which includes two main components: OER must be free of cost and openly licensed.
"Open Educational Resources (OER) are teaching, learning, and research resources that are free of cost and access barriers, and which also carry legal permission for open use. Generally, this permission is granted by use of an open license (for example, Creative Commons licenses)"
OER is often housed in online collections or repositories. Because even strong collections are not always well-crawled by Google, you may have to dig a bit. You can start with a metasearch tool. Tools like the Mason OER Metafinder (below) and OASIS Metasearch will allow you to search across platforms, which can save a lot of time.