I have Niles' Pentatonic Mandolin book and CD. WOW! This little book helped me to understand more improvisation than any personal instruction I have received. But I would not have understood it 6 months ago. Maybe that was the case with your experience. You pulled the book back out when you were "ready" for it and your gray matter was able to absorb it easier. That is what happened in my case anyway.
In any case, Niles is the man! He writes his books the way a genius and a master of any subject does...very simple.
"Only two kinds of people never make mistakes: Dead people and people that do nothing!" [Al's Dad]
'81 Gibson F5L Fern, J Rowland
'07 Arches A Style #11, "Hoss"
'69 Gibson J-50