Stilly, Ron Pen's book was well reviewed by scholars (most notably by John B. Wolford in the Journal of American Folklore, 2013). The half dozen or so reviews I've read have all been very positive.

Wolford summarizes Pen's findings:

"His man mode of communication, whether musically, verbally, or through his woodworking, was an amazingly creative fictive construction. *Even in his extensive and detailed personal notebooks and logs* [emphasis mine - JL] he would construct imaginative fictions that are difficult to sort from fact....

"By allowing others to see him as 'America's balladeer' and a prominent folklorist, Niles arguably did impoverish the discipline's integrity."

Strong words indeed.