It seems obvious that people who are very famous in their field became "very intelligent" because of a combination of hard work and genetics. But it's as if these books capitalize on the faint hope of being a repressed genius of some sort. I highly doubt Einstein or Shannon (as the article implies) ever saw themselves as more than passionate. And the ego required to want to find your inner genius goes contrary to the enormous humility they seemed to display.
That aside, these books and articles all make the same mistake of studying a single person after the fact. It's similar to mimicking Steve Jobs: That's not how he became Steve Jobs. We literally cannot know how much luck was involved in his (or Einstein's) success. Might as well study the lives of lottery winners.
So if not that, how can we maximize our potential and generally better ourselves intellectually? Simply by referring to the very vast fields of learning, motivation and general cognitive science.
But "learn the science" doesn't have quite the same ring to it as "how to be Einstein", now does it?