Moebius Noodles: Adventurous Math for the Playground Crowd, by Yelena McManaman and Maria Droujkova, illustrated by Ever Salazar, is a gift to parents and kids everywhere. The book is full of ways to grow mathematical eyes, with very accessible activities. I wrote about Maria's crowd-funding campaign back in 2011. She raised $6200 back then, and is sending out lots of books to the funders. (Can't wait to get my copy!) If you didn't join in then, you can still buy a copy for $15. If you have anyone in your life with young children, I think they'll love it.
If you're just as comfortable reading your books online, you can get a pdf at whatever price you choose to pay (from zero to infinity). I like this model. When I wanted to read Little Brother, by Cory Doctorow, I downloaded the free copy.I had already bought a copy for my nephew the previous xmas, and wanted to know how good it was before spending any more money on it. I loved it, and didn't hesitate to buy a paper copy of another of his books, Makers. (Also available for free.) I've bought lots more of Cory Doctorow's books than I would have if the free copies weren't available. So we're both happy. And I believe Moebius Noodles will work out the same way. You can download the pdf for free to get a taste. And, if my guess is right, you'll be eager to fork over the $15 for a print copy that's easy to share with little ones.
...watching for a package...

