Parents need to know that there's not much to be concerned about here, but some things may need explanation and context. This takes place during the Great Depression, and your kids may want to know why children are scavenging for firewood in the streets of New York.
This is a well developed book. But its primary appeal will be to New Yorkers who want to understand how the Empire State Building was constructed. It may also fit into a historical unit about the time period. The illustrations are fine. Even up to fifth graders may find this book good because of its informative pictures and text. I just wish there were more books about people who live outside New York City.