There is some distance from this to antenna design, electromagnetism, etc, but I think you have to be fluent in proofs to actually follow along on those. Math is a big subject; ymmv.

A Transition to Advanced Mathematics by Douglas Smith (Author), Maurice Eggen (Author), Richard St. Andre (Author)

ISBN-13: 978-0495562023 ISBN-10: 0495562025 Edition: 7th

It shows up on Abebooks which could help with the price. It's a small book, exceedingly well-crafted and worth every nickel.