Download URL: http://www.usabledatabases.com/database/college-textbooks-from-universities-in-us/
This is a very complete and well structured database of United States universities, departments, courses and textbooks. It has over 6GB of book cover images in addition to 7 database tables (state / province, university, department, course, etc.) and over 210,000 textbook records with detailed information for each of the entries.
Samples can be found by the link. And here are some sample images as well.