Originally posted on Grist:
The project adopts the idea of putting up a bookcase in a public space, in which people could release their used books to be picked up by others. This way of free dissemination, called ‘bookcrossing’, is by now a worldwide movement organised in a central database (www.bookcrossing.com). Registration of books enables following their travels through the world and communication about the books.
In other words, books DO grow on trees! If you want something to read, just go pluck it from the book orchard.