This book is all about how things work. The title gives the book away, but it is an interesting book. The main topics throughout the book are energy, light and temperature. There are many topics within these three main topics that are discussed throughout the book. I found this book very interesting because it takes very complex ideas and puts them into words that children can understand. This book is 21 years old, but that does not take away from the great information inside. I would like to see the pictures with a little more detail, but that is expected with the age. Overall I would suggest this book for upper elementary children to read throughout a semester since it is a longer book. ( )