Good place to get started on communications intelligence -- especially in light of the Bush Admin domestic eavesdropping flap -- that makes Keefe look prescient.
The book is written in entertaining, digestible yet intelligent style, only infrequently forced or self-indulgent. His discussion of the TIA program is hysterical -- and chilling. I didn't mind the self-report/travelogue aspect since part of his purpose is to characterize various sources and 'names' in the field and show how geographically broad it is. That in turn is part of his larger goal: "Just how much of this is paranoid, and how much is reality?" He illustrates that issue and the trouble finding balance by his variably successful efforts to meet people or get information from them. (He comes off sounding like a bemused boy scout at times as he careens among disaffected spies, muck-raking journalists, conspiracy theorists, and the occasional helpful 'grown-up.')
I would have liked more on the emerging technical aspects of Comint, but as Keefe repeatedly cautions, whatever 'they' (officialdom) will let you know about their real capabilities is already ten years out of date; what you can dig up on your own is probably wildly exaggerated -- but you can't be sure. Whenever he gets close to 'state of the art' reporting, his sources worry about exposing their potential profit-margin as much as breaching security. But that's his next book, perhaps. (He also gives the impression he worried about being responsible with what he revealed.)
Recommended -- a readable book that will make you say, 'Yikes!' a couple times a chapter.