I dare say its the greatest math book for teaching the Real Number System of natural, whole, integer, rational, and irrational numbers ever :) At the very least it's a good one
Do Natural Numbers Ever Wonder What's Unnatural?
Journey with the wonderful number one as he travels throughout his Real Number universe to meet a diverse set of Real Number creatures. From the beginnings of his little Natural Number farm though Whole Number Forest, Integer Island, Rational Road and The Land of Irrational, our wonderful number one seeks knowledge.
The story couples cute art and alliteration to create an easy to follow story for you students learning the Real Number System. Educators may decide to use this wonderful guide as either supplementary or primary material for both inner subject or cross discipline learning.