Incarceron: it's a vast intelligent city-prison, sealed off from the outside world and hidden from everybody except the Warden. 
 So it's pretty much inevitable that one day, a way out -- or a way in -- will be found. Catherine Fisher's "Incarceron" is a hauntingly original sci-fi/fantasy story, setting up two very different characters in two parts of a stagnated future world. It's kind of confusing at times, but it smoothly clicks into gear after awhile. 
 Both Claudia and Finn are trapped. She's the Warden's pampered daughter, and is about to be married off to a playboy prince for her father's benefit. He's an amnesiac boy in the Scum gang, plagued by seizures that give him prophetic visions. 
 But their lives take unexpected turns when a prisoner taken in a Scum raid on a train recognizes Finn's eagle tattoo, and he manages to get his hands on a mysterious key that might allow him to get outside -- if he can find the door. And Claudia is plotting with her dying teacher to get a mysterious key hidden in the Warden's office. 
 When the two keys bring Claudia and Finn into contact, Finn suddenly has hope that he can escape Incarceron -- but instead he encounters the true horrors of the secret prison. And in her desperation to avoid marrying the bratty prince, Claudia uncovers a secret plot that her father is involved with... and not only Finn's secrets, but her own. 
 Metal trees, stagnant royal courts, sorcery, creepy old crones and high-tech prisons that always watch with red camera eyes. The world of "Incarceron" is a pretty weird one, and it works pretty well considering it seems to be cobbled together from all sorts of strange sources -- the only real problem is that Fisher takes a VERY long time to mesh together her two main storylines. And I'm still not quite sure what the Sapienti are. 
 Fisher has strangely haunting, vivid prose, with lots of tangled plots and motives, and some moments of pure horror (Finn encountering a vast, freakish Beast made of bugs, dead flesh and metal). While it starts off very slow, the plot really starts speeding up when Finn and Claudia encounter each other, both in the keys and in person. And Fisher manages to throw some genuine surprises into the mix -- while keeping the door wide open for a sequel. 
 Claudia and Finn are likable characters who are both similar and very different -- they're trapped and manipulated, yet they both crave freedom from their terrible lives. Fisher also twines in a bunch of supporting characters whose motives are often murky -- you've got bratty princes, malevolent queens, the icy Warden, the sickly mentor Jared and the tricksteresque oathbrother Keiro. 
 "Incarceron" is kind of slow-moving through the first half, but fortunately there's enough plot, chills and intrigue to make up for that. And I think the story of Incarceron isn't over.