Sound engineering (as opposed to mixing etc.)?
My bible for many years has been
Sound and Recording by Rumsey & McCormick
In its seventh edition so far, it’s a great reference for the science of sound, acoustics, digital sound capture and so on.
My edition is old enough to still have a chapter on styluses but I often refer to it.
Something else worth mentioning is that troubleshooting skills are a must if you end up as a maintenance or design engineer. That starts with understanding signal flow in a system. Then you make determinations as to where you might try and look for problems in a given system.
Beyond that, I would say I learned a lot from audio engineering studies. There are tons of good books in the audio engineering realm that talk about signal flow, how jackfields work, common mode noise rejection, and things like sample rate and audio digitization. All those fundamentals are really important.
This book looks good: https://www.amazon.com/Sound-Recording-Applications-Francis-Rumsey/dp/0415843375/
I don't have all the books I used handy but I'll try and dig them up.