Janitor, its funny that you should mention a Feynman biography because I just checked-out his other one from my university's library. It's called "The Beat Of A Different Drum: The Life and Science of Richard Feynman" by Jagdish Mehra.
The book is a little over 600-pages and only about 100 talk about his younger days. The rest of the book talks about all of his ideas, methods, etc. within the field of physics (electrodynamics, quantum mechanics, etc.). And the way the book is written, each chapter is in chronological order of his life. So basically, you'll learn about the physics as Feynman discovered it. From his days at MIT as a undergraduate student all the way up to his passing in 1988. The book also has many of his formulas and such written out (some with detail on how to do yourself).
I highly recommend you pick-it up from the bookstore or your local library. I'll probably end up buying it myself since its such an informative book as well as biography.
EDIT: I just searched for the book on BN and just found out the book is out-of-print; however, there are around 10 used copies available for sale. Of course, you may be able to find it at a local "used" bookstore in your area.