The title is a bit over dramatic but, per the title, if you could contribute with one piece of knowledge to a book that every single individual should learn from in order to kickstart a civilization, what would be yours?
My personal choice would be the process of soap making, from scratch.
As many works and studies about morality and ethics as possible, because god knows we threw those out the window long ago, and it’s biting our asses now. I’d also add an emphasis on John Rawls’ works, particularly “Justice as Fairness: Political not Metaphysical” and “A Theory of Justice”.