If you are a classics reader, think 1984 by Orwell, Brave New World by Huxley, Fahrenheit 451 by Bradbury, We, etc. These are great books and they will really make you think, but as with many of the classics that you will meet on your required reading lists at school... they aren't easy reading. Be prepared to pay attention and get a little depressed.
Unless you have been hiding under a rock (or have no interest whatsoever in science fiction) you will know that there have been lots of new and popular teen dystopian science fiction published over the last several years. These new novels are a little different from classic dystopian sci-fi, the dystopian worlds themselves have distinct similarities, however they are more plot driven, and thus in my opinion, easier to read. The Hunger Games Trilogy by Collins, The Uglies Series by Westerfeld, and Ship Breaker by Bacigalupi (which won the Printz Award this year) are fast paced, action packed, books that you will have a hard time putting down. Other new and popular titles include Wither by DeStafano and Matched by Condie which are both about forced marriages. Maybe that's the difference, classic dystopians are all about the dystopias, whereas the new teen models use the dystopias for setting and as a catalyst for the plot, but still keep the story focused on the story.
Good reads, either way, but I wonder whether dystopian readers are going to fall into two categories now. I can't say that both types will appeal to the same audiences. Maybe we'll find out at the book discussion? Come ready to talk about whatever type of science fiction you are fondest of, and I will book talk a whole pile of dystopian sci-fi both classic and contemporary.