This book was OK.
O'Neil clearly demonstrates how data can be misunderstood, cause feedback loops or be manipulated to discriminate against people unjustly. This is what the book aimed to do, and it achieves that.
O'Neil does a great job explaining how damaging these algorithms can be for young children, who are being stripped of their precious childhood routines, as their parents have to work bizarre inconsistent shifts.
However, the book often lacks critical thought. For example, although she admits that people draw faulty conclusions from big data, she doesn't seem to consider this when drawing her own conclusions.
She seems to misdiagnose problems as being caused by big data. On page 196, O'Neil says that big data undermines democracy by making a minority of voters more important than others since it allows critical voters in flip states to be directly targeted. The obvious issue here is that Big data does not 'make' these voters more important; it merely highlights an existing problem in the American system.
She too attacks methods that generally seem sound or fails to provide a practical alternative. She points out how poor credit rating causes negative feedback loops, a fair point. However she offers no solution, are we too assume should bank just handout credit to unstable debtors? Furthermore, a few naive gaps at 'capitalism' are sprinkled through the book, blaming it for being the root causes of these issues. However, the details of how capitalism is directly and primarily responsible for such problems are glossed over.
Overall, she achieves her goal of showing how data can cause inequality, but that's all. The book leaves some self-evident questions unanswered and seems to lack critical thought.