Lawyer Bill suggested this one in his top ten list, but I wanted to give it a new thread since I think it deserves it!
I admit I hadn't read 1984 until about four years ago, and I was absolutely blown away. I didn't read it in the context of a class or a group or anyone else's recommendation - just cold (or as cold as you can get with a book already considered a classic).
But 1984 continues to keep its perch in the back of my conscious mind, always popping up here and there when I'm reading the news or contemplating current events, like the oppression by the military junta in Myanmar. They shut down the Internet over there, seriously.
It's a sobering read, but it creates great discussion and is relevant to our lives at any given point.