“The Secret Sentry” by Matthew Aid is a comprehensive new history of the National Security Agency, from its origins in World War II through its Cold War successes, failures and scandals up until the present.

Aid, an independent historian who is also a visiting fellow at the National Security Archive, has synthesized a tremendous amount of research into a narrative that is highly readable and sometimes gripping. All of the familiar stops are there, including the Truman memo of 1952 that established the Agency, the Gulf of Tonkin incident, KAL 007, 9/11 and on to today.

But the book also includes quite a bit of unfamiliar historical material, and almost any reader is likely to discover something new and interesting. I learned, for example, that a few months after seizing the USS Pueblo in 1968, North Korea published a book in French containing the full text of many captured NSA documents, some of which, Mr. Aid says, are still considered to be classified today (p. 142).

What will make The Secret Sentry indispensable to researchers are its nearly one hundred pages of endnotes, which constitute a unique finding aid to the most current archival releases, internal agency histories, and other valuable records. Some of the documents gathered by Mr. Aid in the course of his decades of research later vanished from public stacks at the National Archives, prompting him to realize that some government agencies were silently — and often improperly — reclassifying declassified records. Portions of those now inaccessible records have been integrated into this new history.

Inevitably, the book contains some minor errors. Mr. Aid repeats an assertion by the 9/11 Commission that Osama bin Laden was alerted to NSA monitoring of his satellite phone as the result of a 1998 news story that appeared in the Washington Times (p. 383, note 69). But he neglects to note that this assertion has been effectively refuted. (See, e.g., “File the Bin Laden Phone Leak Under ‘Urban Myths'” by Glenn Kessler, Washington Post, December 22, 2005.)

The author is generous in his citations to the leading authors in the intelligence field, from David Wise and David Kahn to Seymour Hersh and Jeffrey Richelson and other less celebrated writers — with one strange and disconcerting exception. There is not a single reference in the entire book to James Bamford, whose 1983 book The Puzzle Palace, among others, blazed the trail that The Secret Sentry follows. Perhaps Mr. Aid felt it was necessary to ignore Mr. Bamford so as not to be constantly agreeing or disagreeing with him, and confirming or disputing his accounts. If that is the case, he ought to have said so.

The Secret Sentry is being published this week by Bloomsbury Press.