Mystery in the sea. Level 2. Grade 2 and up
The book follows a pair of octopuses that are on a mission to investigate the theft of a diamond. It also lets children learn some scientific facts about marine creatures and their habits while they develop a love of reading and math.
The illustrations, story, and math questions appeal to all types of intelligences so that everybody can find something interesting. This book is translated and published in China.
See sample chapter below and watch intro on YouTube.