I just finished reading Crown of Steel. It was a good follow up to Servant of Steel, and the author Heath Pfaff definitely plays to his strength of writing an interesting and fast paced novel that you just don't want to put down. For the most part I have nothing negative to say, but I did feel like two scenes in particular didn't make much sense for the characters and seemed kind of just thrown-in. But, I will also say that the development of Haley's character and plight was exceptionally well written and I really felt for her. Then, the ending also took me quite by surprise and I've always been pretty capable of figuring things out. It's definitely kept me interested in the series and I will certainly buy the next book.
All in all, well done Mr. Pfaff.