This book single-handedly destroyed my ability to read books without knowing the ending in advance. I can't remember ever hating a book as much as I hated this one (which, I suppose, is an indication of how good it was). I just felt so horribly betrayed by the ending.
I was a freshman in college when I read it and when the character I'd been becoming attached to and rooting for turns his back on everything and gives in I felt angry and hurt and betrayed enough that I literally threw the book across the room and collapsed in sobs. (I never claimed to not be overly-dramatic...)
I understand the purpose behind that ending, and the book itself has led me to a fascination with dystopian novels, but I honestly HATED this. SO much.
Perhaps with a re-read I might change my mind, but I can't get over the feeling of betrayal enough (even after 15 years) to be willing to give a re-read a shot.