The Feynman Lectures on Physics, by Richard Feynman, Robert Leighton, and Matthew Sands is perhaps Feynman's most accessible technical work, and is considered a classic introduction to modern physics, including lectures on mathematics, electromagnetism, Newtonian physics, quantum physics, and even the relation of physics to other sciences. The three volumes were compiled from material presented in a 2-year introductory physics course given in the early 1960s by Feynman at Caltech. Six readily accessible chapters were later compiled into a book entitled Six Easy Pieces: Essentials of Physics Explained by Its Most Brilliant Teacher, and six more in Six Not So Easy Pieces: Einstein's Relativity, Symmetry and Space-Time.
The first volume focuses on mechanics, radiation, and heat. The second volume is mainly on electromagnetism and matter. The third volume, on quantum mechanics, shows, for example, how the double-slit experiment contains the essential features of quantum mechanics.