The books in the Library date predominantly from the 1800s through early 1900s. Some are much older and date back into the 1700s and even earlier. They contain knowledge of skills and techniques that have been made obsolete by more advanced technology.
Some date from much earlier periods because the technology in them quite literally disn’t change in several hundred years. Building a bow to shoot arrows has changed in recent decades due to new and advanced materialsand methods of construction. Without those advanced materials however a bowyer of the 1500s and a bowyer of the late 1800s used virtually identical techniques, materials, tools and skills.
Who needs to know how to make carriages and wagons when automobiles and trucks have replaced them? Horse drawn carriages are a quaint novelty for tourists and festivals. Wooden barrels are a specialized item made only for brewers and landscapers today since we have metals and plastic replacements.
One of the most noticeable characteristics of the skills of the 1800 through the early 1900s is that virtually all of the technology in them can be produced using relatively simple tools. Most early automobiles and airplanes were produced in home workshops using tools not as sophisticated as most hobbyists have in their shops today.
Books on managing a home from the 1800s taught not only how to cook and clean but also how to manufacture most of the supplies and materials needed.
Modern cookbooks provide a list of ingredients which can be bought at the grocery store. 1800s cookbooks often explained how to make or produce all of the ingredients yourself.
Many of the books from those time periods did not assume that you had access to a sophisticated industrial infrastructure from which to procure tools and materials. Many of them were instructions on how to manufacture your own tools and materials.
Books concerning aeroplanes from the pre and post WWI era are at a level of technology which could be recreated by most modern craftsmen. The engines used on most aeroplanes of that era could be manufactured in the machine shops of many modern hobbyists.
The technology of the 1800s through the early 1900s is simple enough that the majority of it could be recreated by any relatively skilled craftsman using relatively simple tools. The tools and equipment needed which are no longer in common use today could itself be manufactured using simple tools.
In short, it is a level of technology that a community of survivors could easily master and recreate using simple tools available in the aftermath of a massive disaster. It would be possible to produce an infrastructure as sophisticated as that of the late 1800s and early 1900s… an industrial infrastructure that in less than 40 years produced nuclear energy and jet aircraft. A technological system that within 70 years went from the Wright Brothers early experiments with flight to putting a man on the moon.
Most importantly it is a level of technology and industry which can be “bootstrapped” by a community of people who have to rely totally on simple tools and their own ingenuity.
It does not require engineers, chemists, programmers and physicists. The first airplanes were built by mechanics and bicycle makers. The first rockets were made by hobbyists and tinkerers.
The technology in most of the books in the Library is well within the reach of most craftsmen, tinkerers and hobbyists who have basic tool using skills. It is a level of technology that is surely well within the reach of a community of people trying to rebuild a collapsed industrial world.