I have just re-read "Folk Song in England" by AL Lloyd(1967) and a very interesting book it is too, especialy the long sections on the evolution and proporgation of "Big Ballads" and "Lyrical Songs and Later Ballads".

A quote on the back from the Melody Maker:

"It is unlikely during your lifetime any book on folk music half so important as this will be published"

Has this been proved true and if not, which books are have proved important?