Everyone gets something different out of a book. The opinions here are mine only.
The author’s aim in writing the book was to stimulate discussions on the reasons for human cruelty (or treating other humans as objects) from a realm of science. The focus is on studying empathy and the social and biological factors contributing to it. Zero degrees of empathy (or being at the lowest end of the “empathy spectrum”) is what leads to “treating people as objects”.
What is appealing about the book is that it is concise and presents the explanations in an easy-to-understand and structured way. The author presents an “empathy spectrum”, with the shape of a bell curve. He also introduces another spectrum, representing degrees of “systemizing”, which is also bell-shaped. The human mind looks for patterns and ways to systemize information. A high degree of systemizing can indicate strength in mathematics, science, music or other systemizing fields. However, extreme (high) degrees of “systemizing” can be associated with Asperger Syndrome and classic autism (an example of a symptom of this is going beserk when something is not exactly in its expected place in a room).
Those with zero degrees of empathy can be “zero-negative” (no positive effect) – this includes borderlines, psycopaths and narcissists. On the contrary, others with zero degrees of empathy can be “zero-positive” (with a high degree of systemizing) and therefore with extraordinary abilities but who also treat humans as objects.
The very last section of the book talks very briefly about the importance of empathy (perhaps just for completeness), but for a discussion on this, I would read books by authors such as Daniel Goleman and Stephen Covey who tackle this topic in depth.
The book provides valuable insights through scientific study. For a lay person like me with an interest in the subject, the simplicity of the presentation (apart from a few pages with technical terms on parts of the brain) made it a fascinating and enjoyable read. It is peppered with many true stories and examples to illustrate the points.