INCARCERON by Catherine Fisher

Set in the not too distant future, Incarceron is a prison that was created centuries before the book begins.  Originally intended as a perfect place--a utopia--Incarceron is anything but.  People run in gangs, and violence and danger are everywhere.  No one is to enter, and no one has ever escaped.  Maybe.  Finn, a teenager, lives in Incarceron with no memory of his childood, and is convinced that he came from the outside.  He is determined to return there. 

Claudia, the teenage daughter of the warden of Incarceron, is also trying to escape--from an arranged marriage with an older man.  She discovers a mysterious crystal key in her father's study.  When Finn discovers a matching key in Incarceron they discover that they can communicate with each other.

INCARCERON is one of the many dystopian novels that have been published recently, and it's a good one with lots of good versus evil action and even a bit of a romance.  First book in the series.