A WMD, or weapon of math destruction, are usage of algorithm that end up being discriminatory toward some people, or that cause problem with their wide scale deployment. For example, an algorithm that identify poor people can deny them services that help them, making them poorer. The algorithm prediction become self-fulfilling and prevent people from improving their condition.
The premise of the book is very good, and there are indeed a lot of good example of how misuse of big data algorithms can wreak havoc among society. The problem is that the author indignation push her away from what should have been the main subject of the book.
In the course of the book, the author raise a lot of recurring problem with WMD, like the "Flock of the feathers" generalization, the "self-fulfilling" prediction, the "discriminating proxy variable ", the "non-appealable conclusion" problem, the "non-measurable important factor". But those categories of problem, which, in my opinion, should have been the focus of the book, take a backseat toward the real subject of the book: how much the United State has social problems.
Each chapter is written to for denounce a specific social problem in the US, like predatory ads toward the poor, racial discrimination toward minority, terrible working hour among low wage workers, and so on. Some of those subjects are indeed caused by WMD. But for some, the link with the purported subject of the book is a bit strenuous. In some case, the author even exclaims "well, that has nothing to do with WMD of course". And a lot of time, WMD are not the root cause of the problem, they only exacerbate an existing one.
That leave you with a book that is more like a classical sociology book denouncing the ill of the American society, with some talk about big data sprinkled on top. If, like me, you are not an American, you may feel a bit left out by that book. This is a shame, because by refocusing the book on the generic problem caused by WMD that I described above, the book could have had a much broader appeal. Don't get me wrong: The problem O Neil talk about ARE important social problem. But they are very specific to her own country, and the militant tone can become grating. I felt at time that the author was not explaining to me how WMD work and how to deal with them, but was rather trying to force her opinion of how the world should be over me. She was dictating me how I should think, rather than helping me shape my own opinion.
In the end, I would have preferred a more objective tone and a better focus on WMD themselves, with conclusion that can be applied more broadly to everyone, not just US citizens.