... How many of those types of books would assume that you are working with hand tools and scraps of metal left over from a dead civilization, and that you can't order the parts you need to put this together...
I just picked three books at random after a ten second search. Pick a topic. Any topic. I guarantee you can find multiple books on how to do it. From smelting iron to forging tools and machinery.
Believe it or not, the world managed to thrive for thousands of years prior to the last 50 years of dependency electronics. They also didn't
have the things like endless roads or cross-continental railways pre-built to take advantage of their inventions. And you know what else? Much of that knowledge still exists, even if only in books
Should this stupid scenario ever come about, people will
have the same -- if not more -- motivation to redevelop those old technologies. Especially
if they're a maniacal dictator with nearly unlimited resources and
a strong desire to gain a tactical advantage over their enemies.
Despite what you may think, not all people aren't stupid, helpless, or lazy. You're almost as bad as those loons on Ancient Aliens who are convinced that aliens built the pyramids because lifting and carrying a stone is hard work. And God forbid someone spend more time doing actual work than fritzing up their hair and sitting in front of a television camera.