Incarceron by Catherine Fisher

I should have known something was up when I had to re-read the first chapter of this book over and over again.  And not because it was boring.  When you get used to certain genres (like YA Fantasy) then you come to accept and understand the simplicity of the plot and environment.  Oh, we're in a castle, I've read plenty of books about those.  Skip five paragraphs of descriptions about gray stones and the chilling drafts in winter and you haven't missed a thing.  But not this book!  Half the story takes place in a living prison called Incarceron and the other half takes place in a distant future where everyone "pretends" to live in the dark ages.  As my mind is still reeling I think I'll go and have a lie down . . .