Maybe 2.5 Stars. 
 I'll get the bad out of the way: I just didn't feel the characters. They weren't developed enough for me to feel invested in their stories. The gravity of the situation wasn't portrayed well. No one was taking the whole thing as seriously as they should. It's world war I, people are dying and being shot out of the sky... the reactions should've been more than: Oh, woops too bad, I hope my friends aren't dead. That's the risk of Y.A.'s; maintaining a serious tone is really difficult. 
 I gave it a 3 because the Darwinist living machines are so fascinating. 5 stars to Westerfeld for thinking up such an amazing concept. 
 Another 10 stars to Westerfeld for giving us a tough heroine in a Y.A. novel. Having to pose as a boy, Deryl swears like a sailor, spits, doesn't take shit from anyone, doesn't swoon at the sight of a hottie, has confidence and common sense. I just wish the character was more developed, she'd be 10 times more awesome. 
 I think Westerfeld had done an amazing job with describing the functions and looks of the Darwinist and Clanker machines but didn't devote as much time for his characters. 
 Have put the next book on my TBR although I'm not 100 % convinced. I'd like to see how Alek's and Deryl's relationship will change once the fact that she's a girl comes out.