Stack the Cats is a charming book about counting and organizing cats in various formations. But when the cats decide to go their own way - as cats often will - it's time to count down until there's only one proud cat and bird left. Counting forward and backward, understanding when there is more or less of something, and grouping and recognizing items are key early math skills for toddlers, making these books as developmentally sound as they are visually engaging.