Fun math books for 8 year old with math aptitude

Question

My 8 year old showed interest and aptitude for math well above the level they teach in her school. I would like to find some math books that would spike her interest in math and make it fun for her.

Answer 1

The Number Devil, by Hans Magnus Enzensberger, is an absolute gem, and the first review currently displayed at Amazon is remarkably appropriate. It begins:

I checked this book out of the library to read to my 8 year old daughter (she wanted me to read "Flatland" to her and I thought the dated language might get in the way). She loved it and now I plan to purchase two copies; one for her and one for my 12 year old son. The book jacket decribed the book as a cross between Flatland and Alice's Adventures in Wonderland. I would have described it as a cross between Flatland an[d] The Phantom Tollbooth, but, no matter. It definitely provides food for thought for any reasonably inquisitive child; and may provide more for a child already interested in mathematics.

I have no quarrel with any of this.