Elsie Lincoln Benedict was considered the world's most famous lecturer during the 1920s, speaking to over 3 million people in her lifetime and writing on what Napoleon Hill and Dale Carnegie and a long list of men would do later. She was an American suffragist leader, representing the State of Colorado for the Women's Right to Vote. Benedict was a pioneer and well respected expert in the fields of psychoanalysis, sociology, and biology.

In this book, with the help of her husband, Ralph, she posits a theory that all humans can be divided into five types. According to her, being able to judge what type a person is, by his outward appearance and actions, will allow one to analyze them .... on sight!

As she says in the Preface, "From this book you are going to learn which type of car you are and the main reasons why you have not been getting the maximum of service out of yourself. Also you are going to learn the makes of other human cars, and how to get the maximum of co-operation out of them. This co-operation is vital to happiness and success. We come in contact with our fellowman in all the activities of our lives and what we get out of life depends, to an astounding degree, on our relations with him."