It's called Fengbo Bookstore, formerly called Fengbin Bookstore.

Walk on the main road south of Yuejintang, the gate of Peking University. After the playground, you will see a door-usually watched by the police, and then turn left, which is also a main road. Go straight and you can see people selling waste products and vegetables and fruits along the way. Go on, you can see it on the left side of the road, and you can see a laundry next to the bookstore (I don't seem to remember it clearly). If I'm not clear, you can go along the road.

There is also a bookstore called Lin San, next to the bathhouse and Huimin canteen. This is easy to find. But the bibliography is not rich and complete.