I can suggest that you check out paperbackswap.com. I've belonged for 2 years and don't remember policies, and they may have changed. I do know that they say books have to be in good condition with no writing and no missing covers. You can request that a book come from a smoke free or pet free environment.
So far all the books I've gotten have been hardbound, my choice. And most have been like new. Seems that others also read a book once and then trade it at paperbackswap.com
The library is a great place to get books also, but sometimes my library system does not have a book available. Just today I tried to get Annette Ornelas' book Peeled-Back Patchwork Curves Without Piecing but it isn't in the system, maybe it is too new.
warm quilt hugs, sue