Wow, this was a surprisingly good read! 
 Trella is a scrub. She works on the lower level of a community where she and her ilk do the dirty work that keeps the operation going, mostly for the benefit of the Uppers. Known as Queen of the Pipes, Trella's job cleaning ductwork also allows some privacy, as she finds places to hide. To help her only friend, she becomes involved protecting the Broken Man, a prophet who preaches about a mysterious Gateway. Then the trouble begins. 
 Having just finished this last night, I have a lot of thoughts swirling around about the ending. I'm so glad no one spoiled the story for me; what Inside is all about; how they go there and why... it was a mystery up until the end (and is still somewhat of a mystery the is sure to be continued through the next installment). I don't want to spoil this for anyone else, but for those of you who enjoy dystopian, futuristic novels, you may enjoy this as well. I am looking forward to the sequel (especially to find out how the relationship between Trella and Riley pans out).