Use one of 24 Knetbooks coupons including coupon codes and free shipping deals for May 2017. Today's best deal is a $6 Off coupon code. There's no need for the campus bookstore anymore now that you can get great deals on textbooks through sites like Knetbooks. Whether you prefer to own your books or just want to rent and return them at the end of the semester, they've got plenty of affordable options.