AbeBooks 10% off Coupon Code (No Minimum Spend)
Just in time for back to uni/summer semester or just for your random reads.
10% off code for the book only, not postage costs.
Try to upgrade to priority shipping which seems to be free over standard shipping.
Unsure of expiry.
Works for the Abebooks.com US site only, so unfortunately it can't be combined with cashrewards 3.5% for the UK site.
Remember to check on Booko.com.au first to see where it might be cheapest (not necessarily AbeBooks).