Dabeiyao takes the subway Wangfujing and gets off at Wangfujing Xinhua Bookstore, and then gets off at Xidan and Xidan Book Building.
The size of the store may not be suitable for you, but also depends on what books you buy. In fact, buying books online is the most labor-saving and affordable, generally below 20% discount. Just go to the bookstores in the above two places.