Reading a book

I recentry became to think that the good books aren't the medium through which we just get information easier or learn some new knowledge. Rather, good books ought to give reader restricted information dpending on the reader's comprehension of the time. In other words, same books are able to be read by a reader at several ages or a variety of stages of one's life. I can hardly imagine other medium having such ability. I'd like to think more about this characteristic of books if I'm working in the publishing.