The Feynman Lectures on Physics are now available in their entirety online and for free. “First presented in the early 1960s at Caltech by the Nobel Prize-winning physicist Richard Feynman, the lectures were eventually turned into a book by Feynman, Robert B. Leighton, and Matthew Sands. The text went on to become arguably the most popular physics book ever written, selling more than 1.5 million copies in English, and getting translated into a dozen languages.”

Source:  ResearchBuzz, Tara Calishain, Sept. 2, 2014