The author got started on the US version of the British ZX81 computer. Horrible keyboard and version of Basic, but cutting all those corners to get the price down made an opportunity for a lot of people to get into computers at just the right moment!
Where to start and what to learn these days is almost overwhelming. It’s a good and a bad thing there is so much that is so accessible now.
I still have the manual on my bookshelf - and as a matter of fact I'm having this print framed at the moment: http://www.alisoneldred.com/john-harris/fine-art-prints-1/sc...
Just as you say, it feels as if I'd need another lifetime to get a comprehensive understanding of a single modern machine.