Hi,
You could try a USPS Padded Envelope approximately at a flat $23. But we strongly suggest to ship books in boxes.
https://store.usps.com/store/browse/usp ... d=P_EP14PE
You can ship via fedex as well for around $40 in a box we offer.
But ultimately you would need to decide if splitting your shipping would might be a better idea.
Sincerely,
Joe