Mika has never gotten over the death of his twin sister--mostly because he's positive she's not dead. He can feel her out there, somewhere, and it's up to him to find her. It's not easy, when the world is surrounded by a giant wall to keep out the plague-ridden animals, and going to school now means drinking cups of the vile FitMix and going to FitCamp. When the new Podfighter game comes to the arcades, Mika takes to it like he's been playing all his life, and there's something about it that will bring him closer to his missing sister. 
 Hmm. I didn't love this. I didn't even particularly like it. There are some huge plot holes (have Ellie and Mika always been telepathic? (view spoiler)[How is the competition rigged so that only mutants make it all the way through? (hide spoiler)]) and abandoned plot threads (where did Helen go? Will she be back?) Maybe some of this will be addressed in the sequel (due out Feb 2012, it seems) but I'm not inclined to pick it up and find out. 
 So: the world has been reduced to the space inside the wall, safe from the plague-carrying animals and the dangerous, deadly nature. Inside the wall, people are packed tightly together in strict classes, with little in-between: the wealthy live in the Golden Turrets, the luxury apartments; the poor live in the slums in tiny fold-down apartments prone to mildew and dampness; the really poor live in the Shadows, where they frequently die of illnesses induced by living in mold and dankness. You've got your garden-variety class issues, plus environmental ruin, population control (Mika and Ellie are among the oldest kids around after a 30-year population halt), gaming culture, conspiracy, and technology (anti-aging drugs, hovercars, tiny pocket-sized "companions" in place of phones). 
 Middle-schoolers may be excited by all the action; high schoolers are more likely to be jaded and bored by the loooooooong details of podfighter tournaments. Similar to Ender's Game or Epic(video gaming), X-Men or Witch and Wizard (mutant powers), Uglies (flying sequences; going beyond city limits), Maze Runner (safety only inside walls), or Inside Out (discoveries about the world outside).