Picked this up on the "New Arrivals" shelf at the bookstore and my 4-year-old loved it right away. It's by David LaRochelle with illustrations by the great Richard Egielski. It's a funny little fairy tale. The twist is, it's told backwards. It begins. "They lived happily ever after because..." then you turn back and back until you find out how this wackiness all began. Of course you'll find yourself reading it from back to front again and again.
We were discussing cause and effect with my second graders so I read it to them. It was perfect for the concept and they loved it just as much as my daughter and have asked for a rereading every day this week!