Amazon offers $10 off your next order when you sign up for a Free one month trial of Amazon Prime. This offer is good through July 28 and is for new members only. You will be charged $79 at the end of your first month unless you cancel your membership. [Amazon Prime FAQ's].
A word of warning: if you're a book junkie, Amazon Prime will put you in the poorhouse. The allure of free two-day shipping will have you ordering books at all hours of the night. Be sure to cancel your membership at the end of your first month.