This is the 3rd book by Ms Fausto-Sterling which I have read. Without question, for me this was the easiest one to read. Ms Fausto-Sterling is by no means a light weight. She is a biologist, feminist and historian of science and is Professor of Biology and Women's Studies at Brown University. Putting it as an understatement, she knows of what she speaks. And of what she speaks, with great authority, are the multiple factors that go into the formation of what is commonly called, "gender." Most of us have an everyday sense of what gender is. In a sense, it is a throw-away concept, for example, baby boys wear blue, baby girls wear pink. Girls can't throw a baseball nor a football with any kind of authority. It's a "boy" thing. Boys who can't throw or have interests that lay in what is stereotypically the realm of the "female gender" are called sissies. The reverse are called "tom-boys". As is her wont, Ms Fausto-Sterling brings a multitude of sciences and research to bear on this notion of "gender." She looks at studies done under the auspices of biology, neurology, psychology, anthropology and even history, to bring the reader to question just what s/he actually means when using the word, "gender."This is a phenomenal and thought provoking book. AFS manages to bring into question everything we think we know about gender and so-called gender-based differences.AFS is usually not all that easy to read. She does her homework and, as in her previous two books, "Myths of Gender," and "Sexing the Body - Gender Politics and the Construction of Sexuality," her notes, graphs, references and suggested further readings (I immediately bought three of them) tend to take up at least as much space as her text, if not more.One thing is certain, when you read a book by Anne Fausto-Sterling, you know your are reading the work of a very serious scholar. She looks into details that may not even occur to the average reader. She also points out flaws in previous research which leads her to question some findings.One aspect of this newest volume that is new to me is that she shows a sense of humor. Maybe I just missed it in her previous works, but it is a welcome addition here. This adds to the readability of the volume. It seems written for the broader, more general audience. My opinion is that she succeeds at that goal.If you want to begin to explore the issue of gender/sexuality, you can do yourself a service by beginning with this volume. Since it is full of references and notes, you are furnished with many tools as to where to go next if you want to continue your exploration. I love this book and will likely read it again.