This is a book certainly worth reading for anybody interested in the subject of signals intelligence in general and the Echelon program and the National Security Agency (NSA) in particular. Writer Keefe does a brilliant job of describing Echelon -- a worldwide listening program jointly conducted by U.S., Canada, U.K., Australia and New Zealand. But beyond that -- possibly because what is publicly known about Echelon would not fill a very big book -- Keefe gets into the philosophical, moral and practical aspects of signals intelligence and its pursuit under NSA. Unlike some other authors who write about U.S. intelligence operations, Keefe does not seem to have an anti-intelligence agency agenda. He is objective to a fault, but presents all sides of the issue. Which is not to say that he doesn't have opinions -- he does, but he seems to base those opinions on evaluating all perspectives first. And in addition, he does a very thorough job, relying not only on secondary sources, but spending a heroic amount of time speaking to diplomats, intelligence professionals, scholars and anybody else who has something to say about the issue. He quotes a former head of the NSA who said that America will have to decide where to draw the line between liberty and intelligence. It's the key question of the book and it doesn't get definitively answered. This is a very well-done book about an extremely important subject which affects the lives of all people -- even if you don't know what "sigint" means.