Little Kids First Big Book of Why (2011)

The best first reference book for the age when every sentence starts with why. Amy Shields starts from a child's own world, with questions like why do I have a belly button and what makes a plane fly, and answers each one in a short burst of text beside a big, clear photograph. Hands-on activities, simple recipes and crafts turn some answers into something to do that afternoon. It is aimed at preschool to second grade, so it works as a read-together book at four and a read-alone one by seven.