You might have to shop around - it was published by Newnes, but typing that into a search this evening it seems copies fetch over £50 on the usual resellers, which seems a bit rich (my copy is marked 19.95.. a 2006 print.)
JL Hood also wrote 'The Art of Linear Electronics' (not to be confused with Hill&Horowitz mighty tome!) and this is a slightly fuller treatment, but came earlier: so deals more with analogue electronic design, and component-level circuits, and slightly less on the audio amp examples side.
If you find one at the right price, you are not missing much from the other.
ETA: well that'll be why: the iniquitous bastards at Elsevier now control the imprint as Newnes:
https://www.elsevier.com/books/valve-and-transistor-audio-amplifiers/hood/978-0-7506-3356-7