During lunch break, I saw this bus in my area. It was there a few weeks ago, so I assume it makes its rounds through Bangkok.
Bangkok World Book Capital 2013 European Union
Engine is running, door is not locked (I can see the latch is open) I can't see anyone inside through the front window, when when I walk around someone opens the door and beckons me to come inside. Aircon, take off your shoes. I go in and have a look and a chat with the operators (they speak reasonable English).
Most of the books are in Thai, there are only few books in English nothing noteworthy.