Nasty But Useful Science: Farts, Vomit, and Other Functions that Help Your Body
Pretty much covers the hows and whys of all the grossest of the bodily functions--vomit, gas, pee, poop sweat, pus, snot, cough and earwax. Yum.
Each topic is covered enough to interest the age group intended, the 9-12 year olds (the lexile score on this one is 820 for those who look at those things). The cover and title are 'cool' enough that by merely leaving the book out on the living room table, most 9 year olds will be intrigued enough to pick it up.
There are plenty of fun factoids and definitions scattered throughout and the last few pages include a glossary, recommended further readings, a list of internet sites to check out and an index as well.