The Secret Sentry is out!
It's 432 pages long, so I haven't got it all read yet, but it definitely lives up to its billing. I haven't seen any jaw-dropping revelations at this point, but it provides systematic and comprehensive coverage and there is lots of new information. It will certainly become the go-to reference on NSA history.
On a parochial note: There is very, very little on the agency of primary interest to this blog—its post-1975 name doesn't even make it into the book. Of course, it's not a history of CSE; it's a history of CSE's much, much larger cousin. The book does confirm that the CANUSA agreement was signed in November 1949, however (page 13 and footnote 22 on page 318). Previous discussion of the CANUSA agreement here and here.
[Update 2 June 2009: Done! It's a good, satisfying read. Doesn't have the anecdotal flair of James Bamford's books, but it is well written and provides a more comprehensive, systematic picture. I would have liked to have seen more information on SIGINT technologies, intercept stations, and allied agencies. There is nothing at all on ECHELON and the controversy surrounding that system, for example. Given the amount of exaggeration and nonsense extant on that topic, a reasonable description of the actual workings of the system (along the lines of that in Secret Power) would have been welcome. An updated version of the kinds of information found in The Ties That Bind and The U.S. Intelligence Community would also have been a valuable addition from my point of view. Of course, including all of that stuff would have made for a much longer book, and one that probably would have been less interesting to most readers. It has 96 pages of endnotes as it is (Heaven!), and I'm sure the author was already testing his publisher's forbearance sorely in getting them to go along with that.
Bottom line: The book is essential reading for anyone interested in this topic.]
Full disclosure: I am one of the many people listed in the author's acknowledgements.