This is an interesting topic and yet the author does it a disservice by simplifying it. Mozart was prolific, it's true, but he could write a symphony in one go. Literally, he would just sit down and write out a symphony. That's not the hard work the author hints at. Then there are others, such as Beethoven, who was great despite not producing many works. Melville wrote few novels, but one was "Moby Dick". Even the work that was done was most likely a labor of love, so that 99% perspiration most likely wasn't noticed by the one sweating.

Further, I'm dismayed that the author attempts to dilute the intellectual capacity as an ingredient in formulating "genius". Name a true genius and I will name you someone who knew their field intimately. It's simply not the only ingredient.

Instead, I would credit perspective. Alan Kay's "point of view". A genius has a way of going down a path where no one else has ventured before, and does so for personal motives. Most geniuses don't try to be geniuses, as much as chase a star only seen by them.

When Beethoven found he was losing his hearing, he wrote a letter to his brothers called the Heiligenstadt Testament, and said, "... but little more and I would have put an end to my life - only art it was that withheld me, ah it seemed impossible to leave the world until I had produced all that I felt called upon me to produce"