When my son was little, this was one of his favorite books. He would ask me to read it to him night after night...which is a little surprising because the main character is a girl and he didn't gravitate toward girl characters all that much.
I am sure the reason he enjoyed it so much was the prose. Perfectly written in traditional jump rope meter, you can't help but inject a bit of energy and jive into the reading.
While the story captures a very typical childhood scenario: mean old lady everyone is afraid of, it's the wordplay that makes this book so special (at least, to my son).
Capturing the feel of an urban neighborhood, some children will identify with the familiarity of the scene while others will be exposed to an important new world.
Typical happy ending and lesson learned made less typical with a magical touch.