|It's a small, cramped library called KinKon館|
It says 貸本 (kashihon - book for loan) and it's a lending library called KinKon館. It lends manga at 80yen per book for a day. The uncle running the stall is actually really proud of it - that manga that costs 400yen can be borrowed for 80 yen.
To be honest, that's a bit expensive considering that I can get the same book at BookOff for 105 yen (and I won't have to return it). But if you don't want to have too many books in your house, this might be a good option. And anyway, as much as I love BookOff, I want small shops like this to stay in business.
So yes, I ended up borrowing one book - the first volume of One Piece. And I'll probably go back every now and then to borrow manga that I want to read but don't know if I want to own.