This book describes a compelling frustration. All adults were once children. But by no longer being a child, an opaqueness arises. We can't go back ourselves and understand how each of us personally thought at those ages. All we can do, as the book very extensively demonstrates, is run experiments that try to pull back the curtain and test inferences about how kids reason.
The text also has plenty of space on how children learn language. A fundamental property of humans. Yet the analysis of it is so difficult as shown here.
You can read this book as a nibbling on the periphery of the study of the mind and of consciousness.