So this is a topic I've rolled around in my head a lot, especially after reading a few that claim that insider authenticity. My main takeaway is that the realism isn't usually in the big, flashy operations—it's in the crushing, soul-deadening bureaucracy. The portrayal of inter-agency rivalry, the soul-crushing paperwork that follows a field op, the constant second-guessing from lawyers and oversight committees. John le Carré, who wasn't CIA but knew the British side, nailed this atmosphere of weary cynicism and institutional paranoia better than most. Actual former case officers, like Lindsay Moran in 'Blowing My Cover,' show the absurd daily reality: the bureaucratic hoops, the petty office politics, the frustration with a risk-averse culture that stifles the very initiative it claims to want. The 'realism' often lies in showing how unglamorous and politically constrained the work is, which contradicts the myth of the rogue, hyper-competent agent. It's less about tradecraft accuracy—which they often have to obscure or fictionalize for classification—and more about the psychological and institutional environment. After a few of these, you start to see the CIA not as a sleek machine but as another giant government office, just with better security clearances and higher stakes for its internal memos.
That said, the ones that feel most authentic to me are the memoirs, not the thrillers. Even there, you have to account for the author's bias, their need to justify their career, or to settle scores. The culture they depict is filtered through their own experience, which might have been in a specific directorate during a specific era. A Cold War officer's book will show a different agency than one from the post-9/11 era. The 'realism' is always partial, curated, and subjective, which is maybe the most realistic thing about it.