Another reason why you soon pop in, is in the corner they have free books. It's a release site for BookCrossing. The idea of BookCrossing, is you register an unwanted book online, then leave it at your nearest BookCrossing site. The next person to pick up the book then updates the profile using the unique BookCrossing number, and after it's been read, the book is left at another site.
I chose The Olive Readers by Christine Aziz, according to the info on BookCrossing, this book has sat unloved on the shelf since February 2012.
BookCrossing is worldwide, and I think it's a fantastic idea. When I was backpacking (in the pre-kindle day) I was reliant on book swaps in hostels, where if you take a book you leave one. I would have been really interested to see where my books travelled to and what people thought of them.