Chris's answer is right, but it's worth adding that we often use the preposition 'on' in the following way in English. I'm reading a book on history. (History is the theme of the book, and I'm learning about it.) Have you got any books on learning to fly an airplane? (books whose theme is learning to fly an airplane). SO WHEN WE USE 'ON', IT'S OFTEN IN A CONTEXT OF LEARNING SOMETHING FROM A BOOK. BUT: If the subject of the book is very specific, we usually use 'about'. "This book is about the Battle of Hastings." (But we wouldn't say "It's about history", because 'history' is a broad subject). "I'm reading a book about the assassination of Abraham Lincoln." (Again, it's very specific, and I'm not learning how to assassinate people!). I hope that was useful.

This probably means a children's book to teach (practice) counting. For example, it may have pictures and stories involving counting. "The boy goes to the beach. He sees one dog. He sees two birds. He talks to three girls."