FYI, shipping in plain brown boxes is often cheaper then the white priority boxes, which are usually cheaper then the flat rate boxes. Just make sure you tell the PO you still want it shipped priority. I was told this by the lady behind the counter when I took my Bake swap boxes the other week. You can also ship books cheaper by telling them they can ship it as Media Mail. It takes about 5-7 days, I just shipped 6.5 lbs of books for $4, lady said it would have been $11, even as "regular mail". I also wrapped a priority flat rate box in brown paper (still sent it priority) and it was $3 cheaper that the flat rate box woud have been.