According to Yale sociologist Perrow, we live with an increasing number of expanding systems--interlocking webs of smaller units--that, through failure, may bring catastrophe upon large numbers of people. Because some risk is inherent in these systems, certain accidents can be called normal. What concerns Perrow is which systems are particularly accident-prone and why, and what can we do about it. For this examination, he uses some of his own concepts; most important, as regards the relative standing of different systems, are the concepts of linear vs. complex systems, and tightly vs. loosely coupled systems. In the first instance, Perrow contrasts systems that are connected with relatively little room for unexpected behavior (because they proceed linearly from one function to the next) with systems that have more feedback, or whose operation jumps from one linear system to another, or which branch out. The second concept refers to systems that are more or less autonomous--and leads to Perrow's demonstration that the complex, tightly coupled systems are the ones to watch out for. Riskiest are nuclear power and nuclear weapons--where the unexpected can be expected, and too little experience is available to operators. DNA recombinant research is another high-tech example, while marine transport is a more surprising one. (The real culprit there is tight coupling of systems that don't work well together, leaving a virtual free-for-all on the high seas.) Perrow thinks that marine-transport safety (and air-transport and chemical-manufacture safety) can be greatly increased with fairly simple measures. In the DNA and nuclear fields, however, he believes the systemic potential for catastrophe far outweighs the potential benefits. The case is made through chapters devoted to surveys of various types of accidents--from air crashes to a Louisiana lake that disappeared when an oil rig drilled, unsuspectingly, into a salt mine. The results will leave you either scared or reassured, depending on where you started. Informative and persuasive.