House of Stairs by William Sleator
I first read the synopsis for this a few years ago and the concept immediately caught my attention. Set in an unknown but clearly dystopian future, we follow five kids in their early teens who are suddenly dumped alone on a never ending room of stairs. There is a machine that spits out food but only when the group perform certain actions which they have to determine by trial and error. When the machine starts rewarding violence of the physical and psychological types the kids