How did the visit to Boston change Helen's views regarding books?

From the text:

It was during my first visit to Boston that I really began to read in good earnest. I was permitted to spend a part of each day in the Institution library, and to wander from bookcase to bookcase, and take down whatever book my fingers lighted upon. And read I did, whether I understood one word in ten or two words on a page. The words themselves fascinated me; but I took no conscious account of what I read.