This is the third book, but is by both mother and son, is YA, and roughly covers the same time (and some same people) as Dragon's Kin. It could be read without reading that one first.
This one mostly involves firestone, mines, watch-whers, harpers, and the Shunned. Again, people tend to be good or bad, but at the end, the female protagonist, who has been brave the whole time, becomes sappy because of a boy.
It's not bad, and I plan to start the fourth when I finish the library book I'm reading, which has one major element that matches this.