papersky has talked about her spear theory of fiction: that some things are spearheads, emotionally, but they don't really have any penetrative power if you don't have what's gone before serving as the shaft of the spear. A.M. Dellamonica's Blue Magic does a really good job of filling the reader in on what went before it in Indigo Springs--but the emotional weight of who shows up when, who chooses what, relies pretty heavily on the other book.
Which I have not read.
I want to be fair to this book, since it's doing several things well, and the thing it's not doing well--failing to be a second book--is a thing it isn't really trying to do. It would be just as unfair to criticize Blue Magic for not being a murder mystery or a Western. And yet: it is not those things, and if you're looking for them, look elsewhere; and it is also not a book whose emotional weight carries through without the experience of reading the one that came before it.
I was pleased with the fact that the characters in this modern fantasy acted like modern people: they read detective novels and tried to figure out the atomic weight of magical substance and generally were not interchangeable with the 13th century. There were references to past behaviors and decisions, but not as though any group in the book was unchanging in that time period. There were several things to like here. But if you want to enjoy those things fully, get both this book and Indigo Springs, I think.