Google "book swap" or something similar.
There are places online where you can list your books for free, and make a wish list of books you'd like to swap them for.
It might take a while for a swap to happen. It all depends on what you are offering and what you're looking for.
But you only pay the postage to them, and they pay postage to you.
Different sites might work a little differently.
I've swapped alot of books at one site and loved it.
Good luck.