When this book was first written it was hailed as a cutting edge book that not only shook up human analysis with its observations and categorisation techniques but advanced the whole sector forward. Sadly its fame was not to last as new ideas, techniques and methods debunked much of what had seemed so true, although in truth it still has much that is relevant and has many revealing insights. However as a piece of social history it reveals much about the thinking of its time and how we can now understand why they came to such conclusions.