There should be no problem with it. What they mean by circulation is for sale, so unless you're bringing in boxes of same-title books for the apparent activity

There should be no problem with it. What they mean by circulation is for sale, so unless you're bringing in boxes of same-title books for the apparent activity of selling them, I cannot see customs taking them away from you. Just don't bring any plants, soil, live and/or endangered animals or uncooked foods with you. Just out of curiosity, can you list some of the book titles?