In my area we have things called "Little Free Library." It's this tiny little box on a post with a few books inside. I agree, the picture you posted is probably the tiniest walk-in library.
http://farm6.staticflickr.com/5516/9087006202_047e611aeb_o.jpg (Picture of tiny library)
http://farm6.staticflickr.com/5516/9087006202_047e611aeb_o.jpg (Picture of tiny library)