I'd be interested in trying to drag the age range down as low as possible - could 13-year-olds handle uncut OB? I think yes.

I can only speak for myself here, but personally what changed my thinking after reading OB was understanding both how things work, and why they necessarily must be that way and no other. Now when I think about that, I realize it allowed me to completely prune many search trees and redirect a lot of wasted effort "sitting on fences".