First, a free book (by Ken Wheeler) which will cover the basic concepts of field theory.
https://archive.org/details/magnetism1small/mode/2up
Second, a series of ...rants/discussions... (by Ken Wheeler) on the topic. Some have further books referenced which delve into the math.
https://www.youtube.com/playlist...
Eric DollardĀ also presents a lot of excellent information on field theory.
https://youtu.be/4oerceZwiJ0
And, he has books available...
http://ericpdollard.com/books-videos/
Beyond this, reading anything about electricity/field theory from Charles Proteus Steinmetz, Oliver Heaviside, James Clark Maxwell, and Nikola Tesla will help.
https://archive.org/details/magnetism1small/mode/2up
Second, a series of ...rants/discussions... (by Ken Wheeler) on the topic. Some have further books referenced which delve into the math.
https://www.youtube.com/playlist...
Eric DollardĀ also presents a lot of excellent information on field theory.
https://youtu.be/4oerceZwiJ0
And, he has books available...
http://ericpdollard.com/books-videos/
Beyond this, reading anything about electricity/field theory from Charles Proteus Steinmetz, Oliver Heaviside, James Clark Maxwell, and Nikola Tesla will help.