You may be surprised to see Betty Smith's novel about a girl growing up poor in the early 20th century on this list. In fact, it is a stretch to call this "mathematical fiction". However, the little bit of math which appears is cute, and this book is such a classic that I decided to list it anyway.
In Chapter XXII we elarn a bit about Francie's academic experience: three short paragraphs about reading and three short paragraphs about arithmetic.
(quoted from A Tree Grows in Brooklyn)
She like numbers and sums. She devised a game in which each number was a family member and the "answer" made a fmily grouping with a story to it. Naught was a babe in arms. He gave no trouble. Whenever he appeared you just "carried" him. The figure 1 was a pretty baby girl, just learning to walk and easy to handle; 2 was a baby boy who could walk and talk a little. He went into family life (into sums, etc.) with very little trouble. And 3 was an older boy in kindergarten, who had to be watched a little. Then there was 4, a girl of Francie's age. She was almost as easy to "mind" as 2. The mother was 5, gentle and kind. In large sums, she came along and made everything easy the way a mother should. The father, 6, was harder than the others but very just. But 7 was mean. He was a crotchety old grandfather and not at all accountable for how he came out. The grandmother, 8, was hard too, but easier to understand than 7. Hardest of all was 9. He was company and what a hard time fitting him into family life!
When Francie added a sum, she would fix a little story to go with the result. If the answer was 924, it meant that the little boy and girl were being minded by company while the rest of the family went out. When a number such as 1024 appeared, it meant that all the little children were playing together in the yard. The number 62 meant that papa was taking the little boy for a walk; 50 meant that mama had the baby out in the buggy for an airing and 78 meant grandfather and grandmother sitting home by the fire of a winter's evening. Each single combination o nubmers was a new setup for the family and no two stories were ever the same.
Francie took the game with her up into algebra. X was the boy's sweetheart who came into the family life and complicated it. Y was the boyfriend who caused trouble. So arithmetic was a warm and human thing to Francie and occupied many lonely hours of her time.

I'm sure that this would be the basis for a very interesting discussion of whether mathematics as normally presented to children is "cold and inhuman" in contrast to the way Francie made it all about family life, and whether one way is better than the other. To me, of course, mathematics does not need to be personified in order to be interesting. The objects have a life of their own, albeit and abstract one, and the interactions between them are as interesting as (or even more than) the "soap opera" relationships between people. On the other hand, I don't see anything wrong with Francie's fun little game either.
Thanks to Roberta Mundschau for bringing this bit of mathematical fiction to my attention.
Contributed by
Anonymous
This is a truly fantastic novel. While there is very little mathematics in the work, the connection that is provided sheds light on an interesting and unique way to approach numbers, which would be beneficial to many young learners.

Contributed by
Anonymous
One of my favorites  though I'd forgotten the passage you quote about Francie's arithmetic.

Contributed by
Anonymous
I'm not sure if you will count this as math, but there are also some scenes with the lottery board at the scrap yard, where Francie and the other kids go to sell scraps. There are prizes on numbered pegs, and Francie wonders why no one ever wins the big prizes, when it seems like all the numbers should have an equal chance. Later on, she learns that the numbers for those pegs are simply not included in the draw.
Unrelated, Sidney Taylor's "All of a Kind Family" has trace amounts of math in that the kids figure out how much they can get for a penny or a quarter of a penny, or how much time at how many pennies per week it will take to make up the library fine etc.

