Books there are generally 20% off, and the price can be bargained for the appearance. As long as you bargain with the shopkeeper more, you can cut it down. There are several effective facades that are not negotiable.
I suggest you go to Hunan Library (next to it) to check the price of the book you want, and then go to Wangtai Book Market to find the book you want and compare the prices, so that you can have a better idea.
Also, beware of pirated books, there are many pirated books in Dingwangtai.