I really like how this series is developing. There are consequences for actions, and Anne Bishop keeps them tightly logical to the different world she's created. Nice balance between threats and possibilities of change in this book.
Meg and Simon's relationship is evolving, but although it's well-handled, it's not the engine of the book. The evolution of the world they're in is.
I don't want to share spoilers, so I'll just say...I'm enthralled.