I second Winick's suggestion of Dave Harker's book Fakesong and also suggest another 'academic' book: Boyes, G. (1993) The Imagined Village: Culture, Ideology and the English Folk Revival. Manchester: University of Manchester Press.

Also:

Rosenberg, N. (Ed.)(1993) Transforming Tradition: Folk Music Revivals Examined Urbana: University of Illinois Press.

Brian