It's well detailed and a lot more rational than most magic systems. Its tough to say which magic system is the better of Chromaturgy and Allomancy/Feruchemy. But I think Chromaturgy just edges out Allomancy a little. Secondly, I like the characters. Kip is real. A hero with flaws. Just like Joe Abercrombie's protagonists e.g Logen Ninefingers. The best heroes are the flawed ones, I always say. Not the perfect untouchables. Gavin or more correctly Dazen is well developed. Karris, Liv, and Corvan are also great. Thirdly, the plot building. It involves the intricacies of plenty of twists and turns. Plenty of suspense.
Twists that involve the main character turning out not to be who I initially supposed. It's the kind of twist that happens when the good guy turns bad. Here, it serves to make the good guy even better. Albeit with flaws. Superb! Fourthly, I love the setting. Not your typical epic fantasy setting as what you have in the Wheel of Time or Sword of Truth. But more of a post Hundred Years' War setting. It's fantasy with magic and guns, the first of it's kind I've ever encountered. All in all, it's a brilliant piece.