Does anyone know which book this is?

I read this book a while ago, and I can't remember the name of it, or the author. It's teen fiction. The cover is dark, with a lit up ferris wheel on it. (it's not the book by Ann M. Martin.) I can't remember much about it, but it's about a teenager that goes to a carnival or something like that. They are sitting in a booth drinking a Shirley Temple, and then a woman comes and talks to them, and the booth swivels around and there is a different world (or different carnival, or something). That's all I remember...it's kind of a scary book, and in one part, there is a "machine" under the ground that makes everything run, and there are lots of people that are literally part of the machine. And the main character's friend gets trapped down there. Then something happens to make them go home. Sorry if this doesn't make sense, I don't remember much. Does anyone know which book this is?