McNeil compiled a two-volume set called Southern Folk Ballads (August House, 1987-88) - that one is a significant piect of scholarship, although not as comprehensive as even the one-volume Randolph Ozark Folksongs.
August House published McNeil's Southern Mountain Folksongs in 1993. It's a short work and covers very few songs - but McNeil tells a really good story about every song he covers. Maybe it's not comprehensive, but it's very enjoyable and interesting reading.
McNeil is the editor of the August House American Folklore Series, a darn interesting collection of books. He's the folklorist at the Ozark Folk Center, and Mudcatters Arkie and Dale Rose are privileged to work with him there.

DMcG, don't give up hope of assembling a decent folk library. I've done pretty well, and I usually limit myself to $20 a volume (except for the really extraordinary books). If you cruise eBay and the online used booksellers, you can find decent prices for many of the books in the Basic Folk Library PermaThread. I'm in California and I've ordered books from Australia and Great Britain, and found that overseas shipping isn't prohibitive - as long as you're willing to wait.

-Joe Offer-