It may have been a one off but one book I bought from ThriftBooks was really in poor condition. I threw it away and washed my hands!
Overall ThriftBooks is a good source for used books. However, their standards are NOT Amazon standards. I too received a book I would have normally tossed, but it was the only one available at the time (personal memoirs of U.S.Grant, paperback). ThriftBooks has saved me some money compared to the competition; just realized you may get a clunker sometimes. Don’t give up.