I loved this book! The cover, the premise, the world and characters, everything in it was exceptionally written. 
 Although I was a little bit iffy on the whole auctioning slaves part, it was handled in a way that wasn't overly disgusting, brutal, and just plain hard to read about. Sure, they were slaves, but they were more like unappreciated/badly treated servants (with punishments and the likes being handed behind a closed door-meaning it wasn't really shown in this book). So it was kind of weird to read about slaves in a fantasy book, and how it was incorporated in that world. 
 As the summary says, Kestrel buys the Herrani slave Arin once she hears the auctioneer mention that he can sing. Of course Kestrel is intrigued- she lives in a world where music was an important aspect to the Herran culture and it was banned/looked down upon when a Valorian was involved in it but the Herrani slaves play for the Valorians (Valorians can't play instruments or sing but are allowed to enjoy the music). So for Kestrel, who plays the piano, Arin singing is like a piece of a puzzle she has to have. Plus music is important to her. 
 And so, the more times she spends with Arin, the more she grows to like him. I liked that it wasn't instalove, Arin hates her for being a Valorian and her mistress and Kestrel just doesn't want anything to do with him but as they spend time playing Bite and Sting together and going to social events together (him being her escort, seeing as how women weren't allowed to alone by themselves in public), they start to slowly fall in love with each other. And let me just say their romance was heart-wrenching! Kestrel thought that Arin already had a sweetheart somewhere in the city that he already loved but in fact it was just an excuse he used (view spoiler)[to meet with the leader of the Herrani rebels who were plotting to take over the Valorians and take back their freedom. (hide spoiler)] so she was troubled by that fact while thought that she would never feel the same about him and he "didn't want to be afraid to touch her all their life". 
 I liked that the story was told in third person omniscient (told from multiple points of view of Arin and Kestrel), and we get to see how complicated their lives and romance is. Not to mention a look into the world and the reset of the characters. The plot was well executed and I found myself turning the pages to find out what was going to happen next in the story, with the siege and the Herrani's after they put their plan in motion. 
 One thing that I'm still puzzled about is the whole thing with Kestrel surviving the plague, the scar on her forearm as proof. When Kestrel was younger, her mother and Kestrel got the plague and her father brought them a Herrani doctor to save them (because they knew how to heal the plague). But what happened was what bothers me: 
 "My father told the doctor to heal us or be killed." 
 "So the doctor did." Arin sounded disgusted. "For fear of his life." 
 "That's not why, I don't know why. Because I was a child?" Kestrel shook her head. "He cut my arm to bleed the disease. He stopped the blood. He stitched the wound. Then he turned the knife on himself." 
 Something flickered in Arin's eyes. Kestrel wondered if he was trying, as she often did when she looked in the mirror, to see her as a child, to see whatever it was in her that the doctor had decided to save. 
 What did the Herrani doctor see in her? Why only save her and not her mother too, or both of them? He could have decided not to save Kestrel either and he would have died by the hands of the General either way, instead he saved one and killed himself. Death would have been the same outcome for both decisions. Was it because she was a child and he didn't want her to die? Or because he saw something in her that the rest of the people can't see? I don't know why, but maybe Arin knows why he saved Kestrel. 
 Hopefully questions will answered in the next book, like what exactly did Kestrel promise the Emperor? What will really happen to the Herrani people? What will Arin do next? etc. This first book was wonderful and I know that this trilogy will be one of my favorites.