It almost earned an “additional purchase,” but it poked one of my review buttons: even when writing for young children, I think it’s important not to talk down to them.  On p. 12 it states, “Your blood moves around your body in tubes.”  If they’d only added, “called veins and arteries,” I’d be happy.  Instead, they used “tubes” as the vocabulary used in the diagram, index, and glossary.  I think they’re underestimating young readers unnecessarily.