3.5 stars 
 I don't quite know how to feel about the Iron Duke. 
 I really enjoyed Ms. Brook's writing style,the genre (steampunk) is new to me, and her premise was fascinating. Having said all of that... 
 The plot was kinda confusing for me to follow. We have a parallel world which I did not fully understand. I still can't quite picture the horde in my mind and it took several chapters for me to figure out who a bugger was. There were also several scenes that I read that I couldn't quite 'see' with my mind's eye, so it felt like I was just reading words instead of following the story. 
 This is supposed to be a romance (no?) but there was a mystery that formed a significant part of the plot - I enjoyed the bits I could understand. Even though I read the book, I still am not clear how exactly they pieced the clues together....yeah. 
 Rhys, the title character ,is the hero (duh) and a well-written one at that. (What is it with authors writing really good heroes and slightly less-good heroines?)He was a man of honor, although it was a peculiar sort of honor. I liked his characterization. He has an interesting backstory which I felt could have been explored more. In any case, the details Ms. Brook gave of his past was not enough to satisfy me, nor was it enough for me to be able to see why/how Rhys grew into the man we know as the Iron Duke. 
 Mina the heroine was...less well-written than Rhys, but she was one of the better heroines I've read: not simpering, not an idiot, not harsh-masquerading-as-badass. Her backstory was heartbreaking. She was the preoduct of a mating frenzy where her mother had presumably mated with a horde. Unfortunately she was born with horde features,a constant reminder to the people of England what they'd suffered at the hands of the horde; so she went through life a pariah, with people spitting at her in the streets, etc. She was also the reason I almost cried reading this book. 
 But sister-girl could be annoying at times. (view spoiler)[ No, Rhys is not obligated to pay the ransom for all of the boys taken captive by the pirate ship! (hide spoiler)] And a good deal of the misunderstanding she and Rhys had could have been avoided if she'd just opened her mouth and said something instead of being a martyr. 
 I enjoyed immersing myself in the world Ms. Brook has created: the mystery and the romance were engaging enough - but there were several things that detracted from it for me, especially the murkiness of the plot ( others may not have been confused, but several times I was confused ) But I'm glad I read this one. And I'll continue with the series.