Studying the Stalin period was quite difficult for historians prior to perestroika. Archives were closed and there was a definite sense that some historical topics like the Purges, the Molotov-Ribbentrop Pact, or the famine were unsafe. Sheila Fitzpatrick's memoir of being a non-Soviet researcher at this time does note that there was always a danger that an inopportune comment or the wrong sort of attention from the state authorities could cut off a scholar from their sources. She cultivated a degree of personal contacts within the USSR to get around this in her research into Lunacharsky and was helped by the assumption of one critic of current Western historians that S. Fitzpatrick was a man.

Conquest, a staunch anti-communist, obviously could not keep a low profile in the USSR and certainly was not welcome to study there. Therefore when writing his books he relied upon memoirs, reports from foreign embassies, dissident reports, as well as a close reading of open-source Soviet materials. One prominent source base for Conquest was the reports of various defectors such as Alexander Orlov, who provided much of the basis for his claims that Stalin masterminded the Kirov assassination.

This type of source materials is one of the major reasons why Conquest really is not that important today outside of a few largely conservative and nationalist circles. Conquest's books rely upon a narrow and inherently skewed source base that he twisted around his anticommunist theses. It was in the interest of Orlov and other defectors, for example, to emphasize the scale of the Stalin's crimes and the dictator's own involvement as it not only exonerated the defectors' involvement in the regime, but provided Western audiences what they wanted to hear during the Cold War. The opening of archives since 1991 has rendered this problematic use of sources obsolete; many of the monographs on the topics Conquest covered present a far more nuanced and persuasive interpretation of Soviet terror than Conquest's Manichean moralizing.

A grad student in Soviet history in 2017 might read Conquest as part of their engagement with the wider historiography, but most of the academy really does not really engage with his work. One of the ironies is that the older work of scholars who played with the Soviet system like Getty and Fitzpatrick have aged much better than Conquest. This was in no small measure because using actual Soviet sources, even in a very constrained environment, was a much sounder methodology than Conquest's reliance upon sources that were incomplete and had axes to grind.