To Burp or Not to Burp by Dave Williams and Loredana Cunti
What better way to engage a kid with the sciences than through the weird and gross. Its not a new approach by any means but it still works. Lots of cool information in a relatively short book, enumerating the effects of low gravity on various bodily processes. We learn not only what happens to a belch, sweat, etc but why it happens. With photographs and illustrations illustrating the points it's a solid choice.