An emerging development in OER is open textbooks, which are textbooks that are freely available with nonrestrictive licenses. Covering a wide range of disciplines, open textbooks are available to download and print in various file formats from several web sites and OER repositories. Open textbooks can range from public domain books to existing textbooks to textbooks created specifically for OER. Open textbooks help solve the problems of the high cost of textbooks, book shortages, and access to textbooks as well as providing the capacity to better meet local teaching and learning needs.
-- Openstax CNX