College level textbooks in USA are a total racket. The major textbooks come out with a new revision roughly annually, where the material is reorganized enough to change section and exercise numbers. The purpose is to destroy the used textbook market, as assigned reading and homework will not correspond to older revisions of the book. Then students are forced to buy new books and the publishers can make big profits.
Checking the situation now, some are even available online, eg:
http://antena.fe.uni-lj.si/literatura/ed.pdf
Some are even unchanged from my times: https://www.fe.uni-lj.si/mma/Osnove_elektromagnetike_2016-02... (1999)
Basically, noone really cares.