Somehw this volume is darker than the original Something is Killing the Children, and that's obviously saying something. But the horror is just so much more personal, with Jace fighting for vengeance and for his family (two families!).
I like the first book first, because it makes heavy use of Aaron, and so revisits a character that came and went much too fast in the core story. But Jace is an interesting story too, and moreso what his story reveals about the monster hunters, their various orders, and their relations with other houses.
Overall, a great book for expanding the universe, though not quite up to the original.
(And definitely the better part of the House of Slaughter spin-off. The alternate issues, presumably to be collected in a different volume, were not worth reading.)