you can go online to usps.com and estimate the cost by size of box or what it appox weighs. I had 5 books shipped to me and it was just over $5. or you can do a flat rate box and it is one prices regardless of weight
umm if you send books "media mail" its 2.53 for the first lb and .40 cents for every lb after that i believe. I send books alot and i just send a heavy box set of 6 books for under 5 bucks. make sure to send it "media mail"