So our little village library has started putting these up everywhere...mostly other small villages that don't have libraries, but also in ours....there are lots of people who for some reason or another do not have library cards, but love going to these and seeing what's in them.
You can take anything from these boxes....you can leave other books you have already read, it's always changing, you never know what book treasure you will find. I am responsible for reorganizing a couple of them in a village that's on my way to work, and it's fun to see what missing from the last time I was there or what's been added. I have seen this done in other cities and countries, and I just think it's so great we have started it out here.
Happy book treasure seeking!