If I remember one of the interviews correctly(it was a Convention panel featured on the front of the JB site I remember) The Cinder Spires might have come from one day when Jim was driving a bunch of kids home from a LARP. He mentioned that in his rear-view mirror he could see in the distance a tornado or something behind him and he thought, "What if that was chasing me?"
Wherever the series comes from, I'm sure it will be awesome.