The Secret Services Handbook by Michael Bradley
It’s the sort of book your grandmother buys you after you tell her you just got done watching the new James Bond movie.
Is it terrible? No, it’s just that kind of book though. There are things for folks like me who have an interest in espionage history/contextual details but for a straight cryptology buff it will not be interesting.
In brief it gives an overview of the intelligence groups of about 12 countries, think Wikipedia but in paperback.
I don’t recommend this book but I read it and I’m keeping my copy. If you’re wanting whatever you can get your hands on information-wise, go ahead and get it but try to find it a used-book store.