Hopefully the people who post on hacker news.
I just bought a book on steam boiler operation and another on building and maintaining internal combustion engines; so, me!
It's a research project, I am mostly self taught and I wanted to build a small archive of materials that would be enough to help a human survive the apocalypse. Farming & Animal husbandry, Metallurgy, Manufacture of goods, Pumps/engines, Electricity, a few other things.
My project is to index the volumes in the next few years and starting some of my own projects, so probably just doing some repairs on small things to start and moving on up!