The author explains why things fail and why design necessitates tradeoffs between performance, cost, and safety. He details methods for identifying and eliminating design flaws and illustrates the consequences when they fail. Lewis examines faulty machine interfaces that cause disastrous human errors and highlights how cost cutting and maintenance neglect have led to catastrophic consequence.

How Safe Is Safe Enough? explores how society determines adequate levels of safety, outlining the announcement and enforcement of safety regulations and addressing controversies surrounding cost-benefit analysis. The author argues that large regulatory effects stem from the public's wide-ranging perceptions of three classes of accidents: the many everyday accidents causing one or two deaths at a time, rare disasters causing large loss of life, and toxic releases leading to uncertain future health risks. The nuclear disaster at Fukushima culminates the discussion, exemplifying the dichotomies faced in reconciling professional risk assessors' statistical approaches with the citizenry's fears and perceptions.

For better or worse, technology permeates our lives, and much of it we don't understand--how it works and what the chances are that it will fail dangerously. Such interest and concerns are at the heart of this authoritative, provocative analysis.