Catherine Fisher's Incarceron was kindly loaned to me by Lady_Shrapnell of So Many Books.
Incarceron is a prison - the only prison - of the future. Sealed away, it is a closed system which nothing can enter or leave. It's believed by those on the Outside to be a paradise, the ultimate in rehabilitation therapy. When all criminals and dissidents were sent to Incarceron a century and a half ago, along with seventy of the Sapienti (the scholars/scientists who designed it) they thought they were creating a paradise from a hell. However, the Sapienti plan didn't work and Incarceron has become a sealed world of savagery where dreams of Escape are the only crumbs of comfort anyone has. To make matters worse, the prison has taken on a life of its own and become sentient.
One young prisoner, Finn, is different to the other prisoners. He has visions which Gildas, the Sapient who belongs to the same tribe as Finn, believes will lead them out of Incarceron, although Finn believes they are memories of his life Outside Incarceron.
Outside is also a prison. Technology has been rejected in favour of an authoritarian and feudal regime (similar to our 17th century) which insists on everything being in Era, a peculiar regression to which the world moved following the Years of Rage (it's hinted that the world went through a major war, which in part led to the decision to build Incarceron and regress to the past. The royal court is a place of intrigue, plots and politics, but Claudia, daughter of the Warden of Incarceron is due to be married to the royal heir, an arranged marriage that was organised after the first heir died of a fall from his horse at a young age. Claudia's intended husband, Giles' step-brother, is a useless brute to whom she dreads being married.
However, both Finn and Claudia find a pair of identical crystal keys that allow them to communicate with one another and they set on a path that will make the worlds of Incarceron and Outside collide...
This was a fascinating book. It's a mixture of historical, Science Fiction and fantasy elements combined. The historical elements are those that relate to the Outside; the SF elements relate to Incarceron, which it turns out, is a vast prison that's been compressed into a tiny cube that hangs from the Warden's watch chain; and the fantasy elements are related to the sensibility that Fisher has adopted. I'm not sure if that makes sense, but the story feels like a fantasy tale but it's got strong SF elements in it.
Incarceron is not a stand-alone novel - Fisher is apparently working on a second book - which is just as well, because the ending of this one is rather abrupt - a cliff-hanger in fact. Claudia manages to use her father's Key to enter Incarceron and bring Finn Outside (she believes he's not really a cell-born prisoner, as others have suggested, but Giles, the royal heir to whom she was originally betrothed), but Finn's oath-brother Keiro and a slave girl named Attia (who had helped Finn and owes him her life) are still trapped inside Incarceron as the Key can only take one person Outside at a time.
I don't think this is Fisher's best book - I've enjoyed others (such as Corbenic) far more, but it is intriguing and thought-provoking.