Also get a copy of https://www.amazon.com/Where-There-No-Doctor-Handbook/dp/094...

Slightly more focused on pediatrics, but super useful resource when other literature says "At this point, head to the emergency room or call 911".

Awesome. Come to think of it, I think my parents may have had a copy.

Beyond that, there would be a ton of information on mechanics and ecology that I couldn't possibly keep in my head. Books on mycology, and other resources that would help in foraging would allow long walks through the countryside to be feasible. As long as one had some way to transport a small library of such materials!