"Spies, Lies, and Algorithms" is an excellent introduction to the practice of intelligence in the United States and is ideal for a college undergraduate or somebody new to reading about intelligence.
Unfortunately, the title of this book is misleading and readers will not necessarily learn a great deal about either spying, the ethics of spycraft, how technology is used, or get an comprehensive overview of the history of American intelligence or any fresh insight about its future. Instead, "Spies, Lies, and Algorithms" introduces several topics related to US intelligence.
While Zegart's overview of the history of US intelligence and commentary are excellent, her insight too often summarizes more in-depth books, which she references, and the conventional wisdom on certain topics. The portions where Zegart describes Tetlock's superforcasting, Washington's spies, or the insight of Kahneman and Tversky simply summarize the key point of other excellent these, and many other, excellent books, providing a reading list for those who are eager for more substance. In other parts of the book Zegart discusses cases that have libraries written about them, such as Ames and Hanssen, without providing a more comprehensive overview of the problem of moles in particular and counterintelligence more generally.
On other topics, Zegart simply repeats the conventional wisdom that other writers and public figures have repeated for years. For example, Zegart examines the assumption that much intelligence is overclassified and cites the millions of intelligence reports the US government puts out each year, but she does not describe the nature of these millions of reports and explain why many seemingly innocuous reports have very high classifications. For example, a sensitive human source of information may tell a CIA Case Officer information that is public knowledge or could easily be inferred, but this raw report, and the derivative reports citing this report from a presumably credible source, will forever hold a high classification due to the great risk to the agent's life if somebody were to tie their information to them.
The problem with overclassifying is largely related to analytic products, which are a very small subset of the millions of intelligence products generated each year. This problem is particularly nuanced, which Zegart misses. A well-informed person, whether they are an academic, a market analyst, or an avid reader of The Economist, will likely often come to the same conclusions regarding current events as intelligence analysts, often drawing on the same underlying information. Any report this person writes would be unclassified, but a report from the CIA, for example, may carry a high classification. This would suggest that the CIA report, at least its conclusions, are overclassified. However, the CIA report likely, and should, include additional specific details that suggest very specific sources of information, contributing to a confidence assessment that differs from what a well-informed reader would come up with. To reach a wider audience, analysts must be trained to use and substitute reports from lower levels of classification that contribute to the same overall assessment. The problem, thus, is not necessarily overclassification, but discipline and training. Analysts may get caught up preparing a product for a particular customer, such as the President or a senior executive, and not consider that their analysis may have a much wider audience that could use the information as soon as possible. If the analyst does not "write for release," anticipating this wider audience, the "overclassified" report may not have the maximum intended impact.
Hopefully Zegart's book inspires people new to intelligence to read many of the books she references, and other to join the intelligence community. While her book lacks fresh insight or nuanced perspectives, her information and analysis is generally very good and she avoids the pitfalls of sensationalism or narrow-minded thinking that befalls other books on the intelligence community. For what it is, "Spies, Lies, and Algorothims" is well-balanced and a good introduction to the "IC" for the casual reader. Readers who have read a few books about the intelligence community, or are serving in it, could pick it up as a refresher, forgive the shortfalls outlined above as those of somebody who did not serve a career in the intelligence community, and learn a few things.
"Spies, Lies, and Algorithms" also leaves out some key topics related to intelligence that would have supported her overall narrative. For example, a chapter describing the intelligence process, from the collection of raw data to the finished intelligence products presented to generals/admirals, bureaucrats, and politicians, would have been fitting.
Overall, "Spies, Lies, and Algorithms" would have worked better reframed as a primer on issues related to intelligence for an audience unfamiliar with the topics. While the title and framing are misleading and the information presented relatively basic, Zegart's information and analysis of key issues are very good and many people would benefit from her book, especially politicians and journalists who often get distracted by the sensational topic of the day.