The story continues, I think this is the most interesting, primarily because of Cinder. 
 Cress is nice, a little too hormonally driven for someone who's never even seen a man...And it's convenient that she's a computer wiz. 
 I like Kai, though he's unnecessarily dense at times. 
 Scarlet is basically not in this book, other than as a tool to show just how evil Levana is. 
 Wolf is cool, I guess. Scarlet needs a boy friend. A haunted, depressed, obsessed and sometimes possessed, boyfriend. 
 Thorne, ahem, "Captain" Thorne is fun. As he is supposed to be. He's probably more interesting than most of the other characters, outranked only by Cinder, and maybe Kai, who hasn't had as much screen time in three books as Thorne has in one. (I know he's been in two, but I hate to mess up such a good phrase). 
 Overall I'd say this series is pulled on by story. which is good. None of the characters are bad, some just seem a little unnecessary. But the tale is where it's at. I'm having fun, and I'm looking forward to the climax.