what is the elf on a shelf book about

The Elf on the Shelf is a popular children's book that tells the story of an elf who is assigned to observe children's behavior and report back to Santa Claus. The elf, named Scout Elf, lives with the family and watches their behavior to make sure they're being good. At night, Scout Elf flies back to the North Pole to report to Santa, and then returns to the family in the morning to watch over them again.