Ordered a book at the end of August, book shipped 5 days later and book was marked delivered a week later. So that is the time span you're looking at for free shipping. The textbook cost no more that $21 and it came in great condition.
BUT
The post office didn't deliver my package so that was the only drawback. I contacted the site, they were very responsive and even called me to offer advice and to send another book.
I did receive the book for a great price.