Shashi Book City. There are many kinds of books, and the discount is usually 7 to 20 percent. There are definitely some books to learn Japanese. Walking into the book city, there are some storefronts selling Chinese books on the right hand side. You can go and have a look.
The address of the Book City is at Hongmen Road, just north of Hongmen Road Bus Station. Take Bus No.8,17,31,37,50, 104 and you can get there!