I seem to recall hearing that Valentine Lisitsa would read books while practicing exercises. That doesn't mean I recommend the idea. In looking at the picture he could be reading the music to his left, but more likely is reading the left page of the book. Good luck dealing with this.
He could be if you were just looking at the photo, but I know at that moment, he was not playing Mozart, which is the music on the left. He was playing Dennis Alexander's Rhythm Roulette (Federation piece), which he has memorized. (And is also his most favorite thing to play ever.)