Our capacity for creativity and art comes from both learned and intrinsic qualities (nature and nurture); both qualities we have had since childhood, such as our personality, our values, our emotional canvases, so to speak, and qualities given to us by experience, such as conceptions and preconceptions, abstract ideas, attitudes and emotions towards issues, and our accumulated knowledge about the world. Music is but one way of expressing our creativity. You may laugh, but their is creative expression in engineering, mathematics and the sciences as much as there is in music; these are simply the media through which we express ourselves.
By reading literature, listening to music, studying equations, we are expanding our knowledge of the world, gaining experiences, and thus increasing the size of our creative palettes, and allowing us to express ourselves more effectively. The question of whether books are more or less effective in this regard is moot simply because the book is merely the medium, and it is not the medium, but the original content of the medium that will affect you. It also depends on you, and your approach to learning. Firstly, it depends on what you intend to take from the book. If you refuse to acknowledge its significance to you, or deny it the opportunity to influence you, you will gain less than somebody who seeks to use the book as a conduit to understanding and learning about the creativity of others. Secondly, it depends on the book, and whether the author has anything of relevance to impart to you. In the vast majority of cases, you will not be able to absorb the entire range of ideas presented by the author, but equally, it is extremely unlikely that there is nothing at all to learn. By approaching this kind of broadening of your intellectual scope openly, you will be able to optimize what you draw from it. In essence, anything you learn can only have a positive affect on your creativity. We are all melded from a different mold, and even if we are influenced by similar sources, there is the possibility for huge diversity in our output, because of the host of different things that affect it.
Sorry for the rant...
Personally, I recommend Piano Notes by Charles Rosen and the Alfred Brendel essays, which have already been mentioned.
