Book recommendation for electrical installation wanted

Was this drilled into craftsmen at vocational school?

That's exactly why they learn it from the ground up and have to pass an exam. Good grief, I can also get books and watch videos on how to drive a car, but a.) that by no means means I can actually do it and b.) I am not allowed to do it without a driver's license.
Sure, it is not wrong to acquire knowledge through reading, but please, one should never overestimate oneself.
If it's about saving money, then preparations can certainly be done by oneself in consultation with the craftsman, but everything within limits.
I am sure that no one here has mastered their trained profession solely by reading books or watching DIY videos.

I am sure that no one here has learned their profession just by reading books or watching DIY videos.

Absolutely right! I just wanted to counter the argument "You don't know how to hammer a nail into the wall, so just leave it!" because I find it much more sensible to then show the person how to usually hammer the nail. Or just tell them where they can look it up (Correction: where they can watch the video in which this process is described). I see it that way because I am convinced that even the most skilled craftsman came into the world as a completely clueless person. Everything he can do today he had to learn, he acquired it himself.

And of course you don't become an expert (with > 20 years of professional experience) by reading a DIY book. And of course there are things in construction that really should be done by someone who brings some experience and knowledge. Hopefully craft businesses don't send only their apprentices...