I bought this some time ago and noticed that I never added a review. I am now correcting this error. If you are looking at this, you probably already know who Richard Feynman is. If for some odd reason you don't know who he is and you are interested in learning about how important things that make up our world may work, this is a magnificant collection of lectures from one of the greatest teachers of modern times. Don't worry about the audio quality of the early lectures recorded. You can easily get past some of the audio technical issues by listening to the words and ignoring the hum and level shifting. Ignoring this because of these technical issues is a little like saying that you don't ever want to watch Citizen Kane because the only film print you have is a little scratched (Don't worry, this was only an extreme example. The original CK camera negatives are just fine). I keep this set in my car and listen on my drive to the office. This is not the type of content that you listen to only once and put away. Every time I listen I learn something or think about some problem in a different way. This is a superb collection and should be treasured by scientist and non-scientist alike. Richard Feynman was a great mind and a great person. He gave us a wonderful gift in these recordings.