I really enjoyed this, but was left wanting a little more (good thing it's a series!). Some things seemed underdeveloped - I still don't totally understand the concept of Luna and the Lunar people, or the futuristic Earth for that matter. I grasped the concepts enough to be able to still enjoy the book, but I wanted to know more about how the current global alliance came to be and what other parts of the world outside the Eastern Commonwealth were like. I also wanted to know more about the whole cyborg thing - why didn't people like them? Were machine replacements for body parts common at some point but then went out of style? Cinder seemed more robotic than human at times (like how her brain could alert her if people were lying or show her the news) and that was a hard idea to grasp. Then again, this was almost 400 pages so maybe some things had to be cut/saved for later installments. 
 Those were my only gripes with the book though. As I've noted in plenty of other reviews, I loathe poorly-developed-just-for-the-sake-of-it-romances (particularly in YA books) but I didn't have a problem with the Cinder/Kai connection, because it didn't overshadow the meat of the story - the Earth/Luna conflicts, the cyborg prejudices, the letumosis breakout, and the loosely-based but still cool parallels with Cinderella. Kai was a little annoying at times, but I couldn't always figure out if he was under Queen Levana's spell so maybe that was less his fault and more the author's? Regardless, I'm looking forward to making my way through the rest of the series, which I've heard gets better as you progress.