I really like a book titled A Living Voice: The Frank Harte Song Collection, edited by Terry Moylan and published in 2020 by Craft Recordings, Dublin.

A real classic is Sam Henry's "Songs of the People", by Sam Henry (Author), Gale Huntington (Editor), Lani Herrmann (Editor), John Moulden (Assistant) - University of Georgia Press; Annotated edition (June 1, 2010)