Heres another good read

Check out this book ,The espionage establishment by David wise and Thomas B.Ross
I recommend this especially to those of you not born during the Cold war(circa 1990).Its an older book dating to 1967 but it gives you an idea of how the worlds intelligence agencies worked.All the major powers intel agencies are in it from the Soviet Cheka(KGB),the CIA,Mi6,and the chinese S.A.D.(Social affairs department)You find out quickly that intel agencies never really disband they just change names and personnel.

Exactly, like how the OSS was broken in to the CIA and Delta Force, before they were "disbanded", their ops were the same as those two groups do today.

Sounds like a book I read, going to check it out.