I bought the first-grade one for my MG 1st-grader who has not had much instruction in math and for whom it is not a primary interest (just now learning multiplication and division at home; doesn't yet know how to subtract with borrowing). I like the general style of the book, but it's too easy for her. She said the same thing when I gave it to her to flip through. Just noting this here because it surprised me a bit. I think 2nd grade would be right for her.