These 2 books are excellent, go buy them now!!! Hunter's content has changed the way I think about guitar amplifier design.
Amped: The Illustrated History of the World's Greatest Amplifiers
https://www.amazon.com/Amped-Illustra...
The Guitar Amp Handbook: Understanding Tube Amplifiers and Getting Great Sounds (Updated and Expanded Edition)
https://www.amazon.com/Guitar-Amp-Han...
https://www.starrsguitars.com/