“Harriet the Spy” is about an 11-year-old girl who spies on her parents, neighbors and friends, avidly detailing their comings and goings into her secret journal. When Harriet’s classmates find her notebook and read its remarkable contents out loud, her life is turned upside down. What’s Harriet to do? Has she lost her friends forever? And even worse, does this mean the end of her days as a spy?