Not quite the same enjoyment as reading a real book, Thomas, but the whole John the Balladeer book, including the preface and (original) versions of the short stories is available online:

http://baencd.freedoors.org/Books/John%20the%20Balladeer/John_the_Balladeer.htm

(I say "original" above because the compilation version Who Fears the Devil as printed by Ballantine Books [1964]--the copy I have--which was the first time they were published together as a series, had Wellman modify the stories slightly to have better continuity. In general, the modifications are pretty obvious and a bit clunky, a statement Wellman [I think] made himself in the introduction to the John the Balladeer series above)