I like this whole series of math related books. This one uses the very familiar arguments between siblings as a basis for teaching area. My kids really like it. Check out Leaping Lizards (Skip counting by five's), Spunky Monkeys on Parade (skip counting by 2's, 3's and 4's), Jack the Builder (basic addition), and Seaweed Soup (patterns), if you want more of this type of book.