My Sister's Keeper - Jodi Picoult : If you read the book, watched the movie, and walked out of it utterly annoyed: we are friends. If you haven't read the book and watched the movie: read the book. If you haven't done either: read the book.
Definitely one of my favorites. This book gets you thinking outside of the box. The author has you on the edge of your seat wanting to read more and more of it. This book led me toward more of mystery books and books that you really had to think about.