I loved HowlerKarma's post! It's great that some people like things like this--me and DD are more bookworms. Also, we've done more math books because she's been more interested in that so far, plus it does seem like there are more math books around. However, we have found a couple of books that you might check out: Science Explained--a really nice, far-reaching book similar to the DK books
but connects multiple topics very well (i.e., atomic structure, physics, physiology in some instances)--
http://www.amazon.com/gp/product/0805042369/ref=cm_cr_mts_prod_img

and if your kid has a sense of humor, these are not illustrated but are fun and are probably at the next level or so of reading:
Physics of Superheroes
Physics of Star Trek (plus of course the original Star Trek series is available through Netflix, as an accompaniment)