The 389-page hardcover is the first book in Vertigo's award-winning Fables series to be written in prose rather than as a comic.
It features illustrations by regular Fables inker Steve Leialoha.
The story focuses on brothers Peter and Max Piper, one of whom is fated to become the infamous Pied Piper of Hamelin.
"I knew the novel would be probably centered around the villain in the sense that the villain is the one who starts things in motion," Willingham told Newsarama.
"I saved the Pied Piper of Hamelin, who's been one of my favourite villains of all time in fairy tales and folklore, for a big important project, and this seems to be it.
"Giving him a brother was just a matter of finding a nice bit of serendipity with the Piper name, and deciding that a good sibling rivalry could be a good motivating force for what set the Pied Piper on the road to becoming such a nasty individual."
Willingham's Fables has won 12 Eisner Awards since it debuted in 2002.