Same here. The ZX manual that came with a list of Z80 opcodes was how I learnt assembly/machine code programming. I lived in a real backwaters, and getting the ZX Spectrum as a gift from a distant uncle changed my life.
Had no other books, no community, absolutely no other resources to learn anything. But the ZX and its manuals got me to where I could write machine code programs without even looking up the opcodes.
One of my favourite games was R-Type, and this book is a great read. I'm rationing myself so I have some left for tomorrow evening!