My favorite nonfiction books to read are the ones that I see help my two-year-old son to better understand himself. Hands Can by Cheryl Hudson is full of pictures of real children, and it illustrates some of things he can do.
Sometimes when he does something with his hands, like clapping or carrying or climbing, he notices it: “Look Mommy!” he says, holding up his hands. I can’t attribute all of that to reading the book of course, but I still think it is fun to read a book of realization and also see him discovering himself.