My experience is that I learn the most be reading 3 very different books by different authors on the same subject.
With some things, I don't "get it" with the 1st, but do with the 2nd. Then with a few things I finally get it with the 3rd or from the combined information from all 3 books.
Here are a bunch of different electrical books...
As to the mechanical fastening of boxes to walls, etc., I learned a lot by having a job at a hardware store when I was in high school - I learned all about the various fasteners, drills, tools, etc. Then working construction jobs when I was younger, I learned a lot from the other guys. Also they would order certain fasteners which you don't see in a hardware store, so I learned there are a lot more things out there than what is available in a hardware store - need to go to an electrical supply for example.
As for you learning this stuff, there are a lot of people on the internet who have this experience and knowledge. I would suggest asking specific questions for something like "Mounting electric panel on brick wall?" and then you will get a lot of information on how this can be done in many different ways. If you combine a bunch of questions in one post, many things will not be answered.