This idea has popped up a few times in the city and is now available in Overington Park thanks to the Friends of Overington Park.
From John Neugebauer: Our little free library is up and running in the park, In the playground area. Come and check it out. Right now it is filled from my library which is war, mystery, and mayhem. Diane put in Bon Appetite and Martha Stewart. There are some good reads, check it out.