Libraries frequently have days were they give away/sell at low prices unwanted books. Sadly, it doesn't suffice to get rid of all of them- and then what do you

Libraries frequently have days were they give away/sell at low prices unwanted books. Sadly, it doesn't suffice to get rid of all of them- and then what do you do? You can always sell those books on Amazon (I've seen libraries do it) but it basically requires a full time team to handle listings, sales, shipping, returns, etc.