The document discusses three open textbook models that aim to reduce the high costs of textbooks for students: 1. A site license model where a university purchases access to digital textbooks for a set price per student per course, saving students hundreds per year. 2. An institutional resource model where the university negotiates textbook licenses and facilitates access for faculty and students, similar to the site license model. 3. An openly available library resources model where the library purchases licenses and manages access and distribution of textbooks to further reduce costs by eliminating bookstore markups.