Look who's getting old: Harriet the Spy: The children’s book heroine who observes friends, classmates, and neighbors – and holds nothing back in her notebook commentary – first came on the scene in 1964, when Harper & Row published Louise Fitzhugh’s Harriet the Spy. Fifty this year!! Unfortunately, the author Louise Fitzhugh died in her 40's in 1974, but Harriet lives on.