Unlike the majority of the Faction Paradox novels, Warring States is the only one to feature the Faction front and centre. Set at the end of the 19th century, the story tells the tale of a mysterious casket that appears to contain an incredible power source. The Chinese authorities want to keep hold of the casket, while a member of the Faction covets it. They clash, inevitably.
Mags Halliday is a fine writer, as evidenced by her Who novel History 101 and the setting rings authentic. The characters are well-drawn and likeable where they're meant to be. She has a good grip of humour and the mixture of science and fantasy. Her style flows and is highly readable and some of the concepts, although playing off pre-established elements of the FP universe, are mindbending, which is good.
If there is a failing of this book, it's that the story is built on the ending and I'm not sure that with the cat out of the bag, the story says a lot that will reward rereading. However, whilst reading I enjoyed it very much. (By the way, I meant to give it four stars.)