When I was getting seriously interested in audio in 1977, a recording engineer friend who knew I had an academic background, handed me a book and told me to read it and come back with questions. It was a massive 1800 page book compiled as a collection of questions and answers about every facet of audio. It’s focused on audio production but covers everything imaginable from electronic, mechanical, and acoustic information. The technical level ranges from high school to Ph.D in EE. Published in 1969, some is technically obsolete but still fascinating as history while much is timeless and still relevant
Anyway, I found a free .pdf of it and would be happy to provide it to anyone interested either in a forum post, if allowed, or PM.