In this book, and its prequel, The Covenant Rising, Nicholls has seemingly set out make a world where magic is a part of everyday life. However, he's made some strange choices that cause immersion in the world to be difficult.
1) very few people can make magic, though everyone can use it. It's not clear who's creating all this magic, since very few of the story's characters have any skill with it at all.
2) magic replaces everyday modern devices; as another reviewer notes, the characters even talk about 'hacking' into a communications line.
3) all this while limiting technology to mostly standard medieval fantasy, with a hint of steampunk. The combination is hard to swallow.
Equally difficult is the central plot concept of this book - that the Resistance, caught in a client state between two competing empires, buy an island and plan to move thousands of people to live there in freedom and harmony. It's just not a realistic idea, especially when we learn that the new island is a tenth the size of the existing client state. It's not close to credible that the evil empires would a) not notice, and b) leave the new land alone.
The plot in this middle book does move along rapidly, and most characters remain likeable. There are more than a few too many easy coincidences, and some facile gap fillers that don't really work.
I'll still be moving on to the third and last book, The Diamond Isle, and I have hopes for a satisfying finale, but it's likely not going to be quite as grand as I had hoped, and I find it a bit hard to recommend the series on what I've seen so far.