When Tokyo was being built in the 17th century—it was called Edo then—the city was planned into districts and quarters based of crafts or markets. Starting with the Confucian academy in the late 1600s, Kanda became a center of learning and publishing. These divisions blended and dissolved with the growth of the city. Today, the streets of Kanda are still punctuated by small used bookstores.
As someone who grew up reading, walking into a bookstore in Japan was really humbling. You figure there would be enough information to at least find major categories of books, like photographic books. It is not that easy. If you really want to know how debilitating illiteracy is, visit a Japanese bookstore.