In the survivalist classic, Lucifers Hammer, a nerdy scientist realizes that the most valuable thing to save for the rebuilding of civilization will be knowledge. The information on how to build generators, grow food, treat injuries, prevent disease, build shelters, etc, etc,. To that end, he starts preserving all sorts of useful books and eventually he is proved right in his prediction of their utility.
Someone appears to have taken that idea and ran with it. A collection of .PDFs of various texts, going back quite a ways, on subjects that would be useful if you believe in the ‘we start over with 19th century technology’ scenarios.
I love reading this sort of stuff. While I have no intention of making penicillin from scratch, but I’d be interested in reading how it was done nonetheless.