The basic idea I want to accomplish is a book that contain the core knowledge and principles for reestablishing a free and prosperous society after an extended dark age, where we have forgotten not only how we've done something but that we have ever done something.
Losing the technology for space flight is not hard and it would not take more then 3-4 generations before we would forget that we had ever landed men on the Moon.
While I am not sure we could ever lose semiconductor technology, it would be easy enough to lose the high-end. Semiconductor fabs cost billions of dollars and are giant clean rooms. It would not take too many incompetent people to reduce the yield to the point it is no longer profitable to run them. The tiny die sizes today are easily disrupted by dust, but the technologies of the '70's are more robust. Dropping back to that era in electronics would be annoying but for most things acceptable.
In general it is possible to lose the high end of any field pretty quickly followed by a long slow decline.
Consider I, Pencil an economist attempted to figure out how a simple pencil was made. Bottom line, it is a whole lot more difficult then it looks.
I just ran across someone trying to make his own toaster, from scratch. Getting ahold of the iron ore wasn't too hard, smelting into iron ingots, quite a bit more challenging.
One of my wife's favorite shows is 1900 House, their most important technology was the kitchen stove, it was heat and food and hot water from them. But the thing they missed most was good soap, detergent and shampoos. It presupposes a municipal water and gas supply and a sewage system.
Not only technology but a governmental and economic system to allow that to be built. The Romans built a great public water system that was not exceeded until the addition of chlorination and fluoridation.
The US Constitution is a great way to run a country but it needs some tweaking since I doubt the Founders had considered some of the changes we've seen over time. Professional politicians are a problem, term limits would be a really good place to start, but the real problem is the bureaucracy, I'm not sure how to deal with that.
So after all that rambling the things that seem important are:
A governmental system that allows for personal freedom and defense of property.
An economic system that allows for easy transactions.
A level of technology that allows for long life and an abundance of food and energy.
This is looking to be a big project.