This has been around for awhile - published in 2006 - but Pick Me Up: Stuff You Need to Know has aged really well. It's published by Dorling Kindersley but isn't in their regular tall and thin format. This one is shorter and thicker - 300+ pages - and jam packed of yes, things you need to know. The book is worth its price simply for the graphics - most pages are done as infographics. Taken together it would give me a headache, but each individual page spread is a really good example of what 21st-century designers (and that's everyone online) should aspire to. I need to think about revamping my online professional portfolio with these design tips in mind . . .
But the information here is what children will be interested in, and there's a lot to it. From "Why there's nothing funny about your pee and poop," (p. 134-135) to "Spot the odd one out" (p. 278-279), kids will enjoy this as much as the Guinness Book and learn something worthwhile while they're at it.
This title is definitely on my "books my school library needs" list (starting in 67 days!). That and some Captain Underpants, of course. :)