Your child wants to know what a scab is made of, where the food goes, and whether their heart ever gets tired. Any one of these six satisfies the obsession on its own. Here's the thing worth knowing before you pick: a body-obsessed child is usually chasing one of two different appetites. Some want the gross, the snot and the pus and the farts, told truthfully. Others want the grand, the two hundred and six bones and the life-size skull and the photograph of a real cell. Those are different children and they want different books. This shelf holds both, and each entry tells you which one it feeds.
Think of this as a shelf you scan, because a four-year-old asking where their food goes and an eleven-year-old who wants a photograph of a real cell are the same obsession at different depths. The books sort themselves into two piles. The gross pile is Grossology, which is proper science about snot, scabs, pus, vomit and gas, written by a science teacher who worked out that a child will read anything disgusting enough. The grand pile is Bones and the DK Eyewitness, which are about structure and scale and awe, all life-size skulls and photographs of the inside of you. Human Body Theater sits in the middle and does both, a skeleton hosting a variety show about your insides, which is why it's the one to reach for if you can't tell which appetite you're feeding. Two more things you'd want a friend to tell you. The DK book is a reference to dip into, not a story, so a child given it at bedtime flicks through photographs, which is lovely if you expected it and a letdown if you didn't. And two of these have real age on them: Grossology is from 1995 and its science is dated in places, while the Magic School Bus trip is a 1989 classic that still does the work and still looks like 1989.