A long one, but definitely worth it

I was on a long road trip recently, and I'm really glad I took along the audiobook Incarceron, written by Catherine Fisher and narrated by Kim Mai Guest.  Two parallel stories take place in very different worlds: Finn can't remember how he became trapped in Incarceron, an unimaginably immense, technologically advanced, "living" prison.  Claudia is the daughter of the Warden of Incarceron, and although she lives a life of luxury, she's trapped in a different way - living in a carefully crafted seventeenth-century Era and preparing for an arranged marriage with the nasty Prince of the Realm.  The stories slowly come together when Finn and Claudia find identical crystal keys and learn how to use them to communicate; Finn is desperate to escape to the Outside, and Claudia, convinced he's the true Prince but troubled by her father's secrets, wants to help.  The description of the physical settings and character development are phenomenal, the pace is excellent, and when you find out where Incarceron really is, you'll be blown away!  Now I need to go get the sequel, Sapphique.