The library in question is the Documents webpage of the CIA's Center for the Study of Intelligence. At this site, you can peruse a number of interesting sounding essays, including Intelligence in American Society, Insurgent Counterintelligence, The Vietnamese as Operational Target, Spotting Photo Fakery, and the classic 1950s study on interrogations (advertised as "some guidelines for secret agents," and only declassified in 1996), Defense Against Communist Interrogation Organizations.
I haven't read most of the many, many documents listed there. Their very listing is the fruit of fights over many decades for the CIA to open its files. Everything there should be taken with a generous dose of salt. But, as the publication of the "Defense" essay demonstrates, there is much there of historical and political value. One of the most fascinating documents I came across is a 1978 interview with Richard Helms, the former director of the CIA who destroyed many of the MKULTRA documents. In the interview, he discusses why he did it, and what (from an official CIA standpoint) MKULTRA was all about. It's interesting, from a disinformation point of view. The interview has a lot more: on Nixon, on Chile, and on Watergate and the Church investigations.
Don't forget to bookmark it.