From the London Book Project site:
“The London Book Project is a free book exchange on a massive scale. Using the London Underground as a high speed distribution network, we aim to bring real literature to London’s commuters. Scrap the freesheets – read a free book instead!
Over the next two weeks we’ll be distributing thousands of second hand books across the tube and we want YOU to get involved. If you see one of our books, please pick it up! Then read it and replace with any book of your choice. Let’s make the tube a giant, free library!”
Sounds pretty great to me. Maybe something like this can happen here once we get our streetcars.