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 in order to kickstart a civilization?
My personal choice would be the process of soap making, from scratch.
What would be your contribution?
Ever since covid hit, I’ve been keeping digital copies of several books like the following:
I haven’t gone full “prepper”, but seeing how fast things went sideways at the beginning of covid, it makes me feel a little better to set aside a little bit of hard drive space, just in case.
You can get full offline copies of Wikipedia too, eh? I use Kiwix for most of the stuff on mine.