I often speak (and write) about how drawing is the basic skill of all the visual arts... and it is. In addition to that, one might add that reading is also on that that short list of all important competences.
How is reading essential to the visual arts? The most important way might be how it forces your mind to come up with and fill in details with no external stimulus. In effect, it trains your mind's eye to compose images and encourages an internal dialogue independent of what you see in front of you. I think this is helpful, if not essential in transmitting ideas from your head to whatever type of canvas your art is transferred to.
The images that form while reading, though certainly derived from your real life and visual experiences, can be more reflective of your personality and worldview. You create a world influenced by the abstraction of someone else's words, but the interpretation is all your own. I have to confess that while I have been heavily influenced by silent film in my art (for example), it's the stories I have read throughout my life that bring me to choose one subject over another. The details and the feelings I imagined in those tales are what I try to bring to life in a visual way.