Here are just some ideas...maybe my brainstorming might be way off for your child but might make you think outside the box...
For a child who likes food...
I'm just here for the Food by Alton Brown
"Alton Brown, host of Food Network's Good Eats, is not your typical TV cook. Equal parts Jacques Pépin and Mr. Science, with a dash of MacGyver, Brown goes to great lengths to get the most out of his ingredients and tools to discover the right cooking method for the dish at hand. With his debut cookbook, I'm Just Here for the Food, Brown explores the foundation of cooking: heat. From searing and roasting to braising, frying, and boiling, he covers the spectrum of cooking techniques, stopping along the way to explain the science behind it all, often adding a pun and recipe or two (usually combined, as with Miller Thyme Trout).
I'm Just Here for the Food is chock-full of information, but Brown teaches the science of cooking with a soft touch, adding humor even to the book's illustrations--his channeling of the conveyer belt episode of I Love Lucy to explain heat convection is a hoot. The techniques are thoroughly explained, and Brown also frequently adds how to augment the cooking to get optimal results, including a tip on modifying a grill with a hair dryer for more heat combustion. But what about the food? Brown sticks largely to the traditional, from roast turkey to braised chicken piccata, though he does throw a curveball or two, such as Bar-B-Fu (marinated, barbecued tofu). And you'll quickly be a convert of his French method of scrambling eggs via a specially rigged double boiler--the resulting dish is soft, succulent, and lovely. But more than just a recipe book, I'm Just Here for the Food is a fascinating, delightful tour de force about the love of food and the joy of discovery. --Agen Schmitz "
For someone who loves music or playing an instrument...
maybe the Physics of sound...tons of stuff online to explore and textbooks (at the college level) to be found used.
For the geeky science lover (these you can probably get at the bookstore, library or at least interlibrary loan).
The Physics of Star Trek
Book by Lawrence M. Krauss
or
The Physics of Superheroes: Spectacular Second Edition Paperback
by James Kakalios
What about a stroll through mythbusters stuff (they have various science fair books and other books) to see what grabs his attention.
