Electromagnetic Fields and Energy
Hermann A. Haus & James R. MelcherFrom review: This is the best book I know of on the subject of electromagnetic fields. Profs. Melcher and Haus were superbly qualified and dedicated teachers. The illustrations in the book were all hand-drawn in ink pen by Prof. Melcher. I had the privilege to be a graduate student at MIT in the 1990s and to learn this material from Prof. Melcher and Prof. Haus, so I am very familiar with this book and the teaching style it codifies.
This book is not an easy read at first, but every page will pay off with the insights you gain by understanding their points. The writing is pretty dense, and you are assumed to be comfortable with vector calculus and other mathematical tools. For me the real gems are the beautiful figures, and the many examples and worked problems.
The book will surely reward diligent study.