Disclaimer: I am not an amazon employee, have nothing to do with the company.
Amazon Prime: you pay $79 and get free 2nd day shipping; one day shipping for $3.99...on all orders. You can also "share" your membership with other family members. So, my husband uses it, me, and my parents. Free shipping on things you send to other people, too...ie, all my Christmas shipping was free.
So, now, if I feel like buying a $5.99 paperback, I don't think twice, just click "2 day ship" and I get the book...for $5.99. It's great.
Leslie