Preschoolers probably won't understand all the scientific terms, but they'll enjoy having someone read the amusing rhyming description of skeleton parts to them. Besides the rhymes, each page has both funny and scientifically accurate illustrations and sidebars called factoids that will be of interest to older kids. That information will be helpful in science classes and I even learned some things I didn't know myself. And any kid who breaks a bone would certainly find the book interesting
To be honest I must admit that I know the author, Bill Kirk, and the illustrator also did one of my books, but I wouldn't be mentioning this book if I didn't honestly think it would be a great educational resource and an enjoyable read for kids.
I haven't seen the other books in the Sum of Our Parts series, but if they're as good as this one they must be great.