A text that I use as a supplement for my undergraduate E&M class is:
Zangwill, Modern Electrodynamics, 2013
This is definitely a more advanced textbook than the usual upper-class E&M texts; I'd put it somewhere between Griffiths and Jackson. Where it excels is in the range of applications provided for the upper-level material. A sample of these:
- Electrostatic potential energy in the nuclear liquid-drop model
- Electrostatics of ion channels in cells
- The four-point resistance probe and the method of images
- Focusing by axially symmetric magnetic fields in an electron microscope
- Whistlers
- The classical Zeeman effect
- CMB polarization
Also, it contains the funniest E&M problem I've ever encountered: "Find the lowest resonant frequency $\omega_0$ and the exact half-width $\Gamma$ of the resonant cavity God instructed Moses to build in Exodus 25:10–11."