Girl15 is looking forward to her Naming: she's finally become the Huntress she's been training to be, fulfilling her lifelong ambition. The newly-christened Deuce gets paired with Fade, the loner-outsider who hates everyone in the enclave. Together they patrol the tunnels of their subterranean world, searching for food and avoiding the Freaks. The freaks are mindless, hungry, savage animals, vaguely human-shaped killing and eating machines. On a recon mission to a nearby enclave, Deuce and Fade are surrounded, and they have a troubling realization: the freaks are getting smarter. They're organizing, strategizing. This is bad, and will mean trouble for their Enclave. And the trouble will get worse if the officials won't listen to them. 
 And then things get worse, and Deuce's underground world becomes a memory as she's forced topside for the first time in her life. Blinding bright light and a different kind of violence--but also more of the same. 
 There are two different books here, really: there's the dystopian civilization that Deuce has grown up in, and all the issues there of classism, work culture (AFAICT there are only three career paths: Breeders, Builders, and Hunters, so idk what you do if you'd rather be the cook or something), intellectualism and the isolation of that ivory tower, the unquestionable government that is Always Right No Matter What the Evidence Says. And then Part 2 is the topside straight-up zombie-apocalypse story, which disappointed me because it could have been so much more. 
 Still, it's a great dystopia/zombie apocalypse for middle schoolers, not too horrifically graphic but still with fighting and action galore. (view spoiler)[A touch of romance (WHY WHY WHY WHY WHY does every freakin' apocalypse involve a love triangle WHY WHY WHY) that, thankfully, Deuce doesn't totally realize she's involved in until it's too late. (hide spoiler)] 
 Recommended readalikes: City of Ember for underground society and the need to explore the surface; Divergent for choosing career paths and an unapologetically ass-kicking heroine; Forest of Hands and Teeth and The Enemy for attempts to find a safe haven through zombie-infested areas. 
 And this is BOOK ONE of a new series, even though this ended in a perfectly good place to make this a good stand-alone book. Grumble grumble insert anti-sequel-rant here.