The author does a good job of explaining how people's biases affect their interpretations, though he could do a little better at recognizing his own. But still an important lesson/reminder for everyone. The parts about how many human attributes and diseases actually involve the interaction of many different genes as well as environmental factors is a particularly important point.
The book makes the very valid argument that misconstruing the significance of genetics as many do encourages supremacist views. People use flawed genetics arguments to claim that one race or sex is in somehow superior to another (even though both are discrete categories imposed on Nature by certain elements of human society). It also mentions several times the inaccuracies and guesswork behind many commercial DNA tests, which are not at all surprising.
The book gets things wrong when discussing trans* people. The book asserts that trans* people's identity is at odds with their biology, but it is in fact the gender and sex label assigned to them at birth that is often at odds with both their identity and biology. The book points to the fact that what is commonly called "biological sex" is not a simple light-switch binary, but a complex collection of biological factors that, while for most people are all congruent, for some people are not. Furthermore, it is considered bigoted to call someone by a name that they are not, which the book does at least twice.
In addition, the book largely ignores the wide array of intersex variations that occur among humans to the point of being factually wrong, giving only the most cursory mention of some of the more well-known ones.
I must also deduct points for uncritically referencing Ray Blanchard, a notorious quack.
The book explains well how the concept of race has very little basis in genetics. It demonstrates how race is a social construct, but fails to do the same for gender and sex, which also are. It also debunks the idea sometimes seen in racist arguments that human races are different subspecies.
Later on, the book discusses problematic issues surrounding relating genetics to intelligence, the concept of IQ, and eugenics.
Another issue with the book is that it often assume that everyone thinks/believes in mostly the same way, which obviously is not true, especially across different cultures. There a few points where such differences are noted, but the assumptions then continue unabated elsewhere after that. For example, the author claims at one point "we prefer simple stories" as if this is some fundamental truth about the human species, when in fact a not insignificant number of us (self included) generally do not prefer simple stories! Why would complex mystery, fantasy, and adventure stories/movies/games be loved by many people if everyone preferred simple stories? Despite doing a great job of calling out essentialist thinking, the author sadly falls victim to it himself a number of times.
The book includes a section on genetic engineering and potential issues and considerations around it, especially if applied to humans, but there is also a not insignificant amount of GMO apologism.
In any case, the key message of the book -- that DNA is not some all-powerful unchangeable computer code-like essence -- is certainly sound.