Disclaimer: I received this book as a Goodreads giveaway on the premise that I would review it. My copy was an uncorrected proof, and there may be changes in the final product, due out 10/7/14. 
 Spring has come to Bedlam City, and Anthem Fleet is beginning to recover from the events of the winter. The Syndicate seems to be lying low, and she no longer goes out every night to fight it. But now a new threat raises its ugly head. The Invisible, a group that seems to have a grudge against the wealthy North Siders, is engaging in ever more deadly "pranks." They also seem to have an interest in the New Hope, Anthem's hero identity. Things quickly get personal for Anthem, who is more closely tied to the Invisible than she could have imagined. 
 This is a sequel to Ms. Kahaney's previous book, The Brokenhearted. In that book, Anthem lost her human heart and had an experimental "chimeric" heart implanted by a black market scientist. This gave her enhanced speed and strength, and as of the beginning of this volume, ultrasonic hearing. This is listed as a middle grade book, but Anthem is a high school senior, and there are sexual references and drug use that puts this more in the young adult category. 
 There are a number of flashbacks to the time of Bedlam City's original hero, the Hope, which eventually tie back in to the present day action. Some background is given as to how Bedlam City became so sharply divided between rich and poor, and the Syndicate became so powerful. 
 Anthem is thankfully not as blindingly stupid as in the first book, though this may be less because she's wised up and more because the nature of the plot keeps her from getting too wrapped up in her own love life. She's still a bit too trusting of the wrong people, who go against their own best interests to do the evil thing. 
 The Invisible try to come off as an Anonymous-style social movement, but it is obvious from the beginning that their expressions of regret at people getting hurt or killed are self-serving at best, and their political philosophy is incoherent. Their leader's plan turns out to be nothing less than mass murder for reasons that make sense, but diminish that person's ability to attract empathy. 
 And even when the Invisible have been stopped, Anthem has to deal with another villain who has gone unseen by her. 
 One boggling moment is that the city has two separate power grids, with no way to relay power from one to the other in case of failure. it kind of makes sense the way the background is set up, but a case of cutting off your nose to spite your face. 
 Again, due to the subject matter and themes, I would not recommend this to below junior high readers, and conservative parents might want to skim the book first. That aside, it is better than the first volume in the series and should appeal to fans of action girls.