I second the Bamberg and Sternberg recommendation. Those books are great introductions to differential geometry and E&M. You can go directly to part 2 if you al

I second the Bamberg and Sternberg recommendation. Those books are great introductions to differential geometry and E&M. You can go directly to part 2 if you already have a strong calculus foundation, but part 1 will give that to you and make a gentle introduction to part 2 where differential geometry is explored in more detail.