Amazon has a list of 100 bestseller books in physics category. this includes popularizations, biographies, textbooks, Carl Sagan, Brian Greene, intelligent design, iffy-physics-of-the-supernatural, physics cartoons and comedy, ANYTHING if it has a connection with physics*. So the competition is quite stiff. What fraction of the top 100 bestsellers turn out to be books by or about Feynman? What would you guess? you can check here: http://www.amazon.com/gp/bestsellers/books/14545/ref=pd_ts_b_ldr/102-1454980-4598542 just by scanning down the list. Maybe you wont be surprised. It might be just what you expect. But it surprised me. *they even include a novel by Virginia Woolf called "The Waves" because it has waves in the title.