When You Reach Me by Rebecca Stead

If you like plots that keep you guessing, you might want to give this Newbery winner a try.  Miranda receives a series of notes that appear to predict the future.  The notes ask for her help and state, "I'm coming to save your friend's life, and my own."  The plot works its way through middle school drama, mysterious circumstances, a chance to win on "The $20,000 Pyramid," and, of course, those weird notes.  Things come together in a fast-paced ending that had me going back to find where I missed clues.