Ben Franklin and His Magic Squares
The first half of this reader written for 2nd/3rd grade level tells you about Ben and his rather colorful life. It's a well-done historical sketch that all of my kid enjoyed as a readaloud (5, 7 and 9 at this time). Then, after setting the stage for you that this is one busy, colorful guy full of ideas, they tell the story (probably a myth) of Ben falling asleep during a government session and turning to doodling and math puzzles to overcome his boredom.
The math is wonderful in this reader. My daughter (7) grabbed a pad of paper to copy and figure out the magic square. After finishing the story, they walk you through how to construct a magic square step by step. I read these to her and she enjoyed putting it together, and then we went through and added the rows and diagonals to prove they all added to 15.
The versatility of this for a child her age was the ability practice of all things groups of math facts. This square has 5 in the middle. So each row, column and diagonal consists of 2 addends of 10, and the 5, to equal 15. She is still not proficient in memorizing all of these, so it was fun exploring how each combination added up around the square 6+4, 7+3, 8+2, 9+1. Then we found another pattern in 3 of the rows - you made either 7 or 8 to add to another 7 or 8. The last row was a 9+6 combo which she has learned to approach with the method of taking a 1 from the 6 and adding to the 9 to get 10 and 5.
Nice reader to explore history and math mysteries using math facts.