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.
True … but this kind of knowledge and organization endows some people with power and control over others. Any time any individuals are given power over others for any reason, especially when that power is based on mistrust, falsehoods and outright lies … people tend to abuse that power.