Well, to start with, this wasn't what I was hoping for. I rather like the character idea and was hoping for a book with 'Spring Heeled Jack' as a master villain. Instead we have a group of criminals calling themselves the 'Spring Heeled Jacks'.
That said, the criminal gang was interesting in that it wasn't just a simple gang of thugs, but a group with a mission, a philosophy, and some inventive genius. The quality of the writing and the inventiveness of the scenario mostly made up for my disappointment in not have 'a' master villain.