I think this is a rather splendid idea that is already taking place in several cities around the world.  No memberships, no late fees – you simply take which items you like and go on your merry way.  The only thing the bookcase asks of you is you add a few items of your own to keep the supply replenished.  If I lived in a not so suburban area I may try this but I could just see the HOA getting all bent out of shape over a permanent bookcase on the sidewalk.  Perhaps these are barriers we can work to break down.  It is a lovely idea nonetheless.