Flat World Knowledge - "We preserve the best of the old - books by leading experts that are rigorously reviewed and developed to the highest standards. Then we flip it all on its head. Our books are free online. We offer convenient, low-cost choices for students - print, audio, by-the-chapter, and more. Our books are open for instructors to mix, mash, and make their own. Our books are the hub of a social learning network where students learn from the book and each other"