Here in the United States, the libraries host book sales every now and then. It’s usually a fund raiser event runs by Friends of the library. There are tons of books for sale for a dime a dozen, mostly donated from the public and the money raised from the book sale benefits the local library system and its patrons.
I like to go to this book sales to pick up books. Father in law collects old books, so if I see one that I think he would like, I would buy it for him. A friend of mine actually go to this book sales to pick up books for resell. She has a barcode scanner that she could scan to find out the reselling price of the used books, isn’t that cool. She will pick up tons of books that have good resell values and resell them online!