You might try
WWW.PAPERBACKSWAP.COM.
They are into all sorts of books, not just paperbacks, but also some technical books, manuals, etc..
The deal is it is all computerized so it is a snap to use – you print off the mailing label, pay postage even on this site if you want – Media mail $3-4 to send it, but you get
“ credit “ for a book for someone to send you one !
So overall it is “free” – such a nice four [4] letter word.
Also, they have related sites that do the same for music CD’s and movie DVD’s.
You can” swap “ credits – so for books you could get free CD’s & DVD’s sent to you.
They have been doing this for awhile and they also quickly “weed out” the not so honest ones.
Not international however as far as I know – just USA and a real big growing following !
It all started about “recycling” books so they do not go to a landfill.
Worth a try.
I find it very useful for especially older computer books long ago out of print for my decades of STS-NSF research [science, technology & society – National Science Foundation].
I have always been really pleased – a lot of very nice people from across the country on it.
Good luck !
Frank
P.S.
I got Osborne’s “Hypergrowth” book autographed as well as Carly Fiorina of HP-Compaq fame [or infamy, depending on your viewpoint !]. Survived cancer but did not get elected to public office.