Pack the book that you intend to ship in a polyethylene bubble mailer, mailers that are self-sealing, durable, water-resistant and lighter than manila envelopes and cardboard boxes.
Opt for media mail at your local post office. The cost of media mail shipping is determined by the weight of the package; U.S. shipping zones are not a consideration.
Speak to the postal worker about bulk media mail for future shipments that will include a large assortment of books. This shipping service allows for a minimum of 300 pieces with a shipping weight maximum of 70 pounds.