It's for the kids BECAUSE it's disturbing.

The House of Stairs (1974) (ISBN 0140345809) is a science fiction novel by William Sleator. While it is typically labeled as young adult fiction, it deals with fairly sophisticated issues and has a persistently disturbing tone, so it may not be suitable for pre-teens.
-http://en.wikipedia.org/wiki/The_House_of_Stairs_%28William_Sleator_novel%29