[quarterwave]

Feynman-II has a nice chapter describing the idea of curved spaces: http://www.feynmanlectures.caltech.edu/II_42.html

The chapters on electromagnetism and special relativity are outstanding: starting with why the magnetism we observe around a wire carrying current is a v^2/c^2 effect, and proceeding all the way to how the electric and magnetic field intensities are both part of an electromagnetic tensor. And then the field-versus-potential question, leading to a discussion of the Aharanov-Bohm effect, etc.

The discussion on the classical theories of the electromagnetic self-energy of an electron is outstanding. It's in Vol.II that we really understand how much this guy had thought through the stuff, he wasn't just drawing squiggly lines to calculate some numbers.