I stumbled on a picture book about math at the library that looks promising. My son had just headed off to find a book in the Juvenile-nonfiction:zoology section and I noticed that the next aisle over included math. I first picked up a book with arithmetic word problems (booooring!). Next I picked up Mathematics by Irving Adler, illustrated by Ron Miller. Here is an excerpt from the front flap:
Although mathematics developed along with civilization to help people solve practical problems, many people found that numbers and shapes were fascinating in themselves and began to play with them for pleasure.
and another from the book itself
Mathematics is not a finished subject. . . Sometimes a new branch of mathematics is created to satisfy the curiosity of the mathematician. Then a use for it may be found later.
See my review on Goodreads.