The Earth has been conquered by an alien species known as the Assembly. The adults are brainwashed with the telepathic Tone, leaving only the children. 
 That's the setting of the scifipocalyptic "Midnight City," a suitably gritty, bleak story set in a future world where aliens have successfully conquered the world. While some parts of it aren't well-defined enough (the romance is pretty awkward), J. Barton Mitchell whips up a pretty good story, with a mysterious undercurrent. 
 Bounty hunter Holt Hawkins and his dog Max are on the trail of Freebooter Mira Toombs, so they can drag her back to Midnight City. He does manage to capture her -- although he gets humiliated by one of her cobbled-together devices -- but the journey back is interrupted by a crashed Assembly ship. Inside is a little girl named Zoey, who can't remember anything about her past life. 
 But Holt quickly discovers that Zoey is more than she seems -- she can sense the Assembly, and they are searching for her. As the trio heads for Midnight City, they must grapple with Assembly factions, the insane Forsaken, salvagers on the river and the mazelike world of the underground city. If they can stay alive, the little girl might be the key to stopping the Assembly.. 
 "Midnight City" has a few echoes of previous books here and there -- the "Tripods" quadrilogy and "War of the Worlds," especially when the spider and/or tripod Assembly walkers enter the scene. But the story still feels very fresh and new -- North America is a muddy, bleak wasteland patrolled by aliens, and teenagers slowly lose their minds to a telepathic static. 
 Mitchell has a pretty smooth, strong style, with lots of gun-blasting, explosive action scenes -- whenever things start to slow down, the gang is attacked by Forsaken or Assembly. And he comes up with a pretty decent mystery: who is Zoey? Why is she different? Where did she come from? And just how far do her mysterious powers go? 
 The one problem is the romantic subplot. It's pretty much required now that any series for teens MUST have a romance, so there is immediate tension between Mira and Holt, but it feels kind of rushed. 
 However, they're pretty solid characters in their own right -- she's a master mechanic who likes to cobble together devices out of "artifacts," and he's a grim bounty hunter with a much softer heart than he likes to think. And while children and animals usually end up being cloying and/or annoying in this sort of book, both Zoey and "the Max" are pretty lovable. 
 "Midnight City" has a few freshman bumps, but it's a bleak, adventure-packed story that leaves you wanting to see whatever's next for Holt, Mira, Zoey and the Max.