Surprisingly, his early lecture courses were a bit of a failure. Which is a pity, but the "Feynman Lectures on Physics" are still a great introduction to just about all of physics as it was at the time. Electrodynamics, Fluid Mechanics, Relativity, the Quantum World. It's all in there, and all explained very well. I hope one day I may be able to explain things half as well, and as engagingly, as he could.