I have always tried to steer clear of AC theory stuff which is a bit daft as valve amps don't work without it.
Rozenblit has a no-nonsense style which makes it very easy to learn and digest even complex concepts, without a great deal of pain. You still need to think hard but he makes it pleasureable to learn the stuff.
Jeez, I even enjoyed phasor diagrams and the trigonometry needed to work them out.

One of the best quotes in the book is quite simple,
"Every time one desired parameter is optimized, another is degraded. It all boils down to finding the best set of compromises that provide the best result"
That's why I have had to build so many bloody amplifiers. If as a scratch-builder, you fail to understand the implications of that simple bit of info, you will chase your tail forever like I was perilously close to doing. To be able to choose those compromises, you need to know what you are doing and why. This little volume gives you the confidence that comes with that knowledge..
You never know, I might now be able to design and build amps for the pleasure of the sound they give rather than design amp after amp, with an increasing sense of desperation.

Nuff said, and at £19 from Amazon it is a no brainer.