The Gulag Archipelago is a work of fiction from a Nazi sympathizer, so that makes sense.

Even Wikipedia can’t hide that Timothy Snyder is a hack:

Omer Bartov wrote that “the book presents no new evidence and makes no new arguments”,[28] and in a highly critical review Richard Evans wrote that, because of its lack of causal argument, “Snyder’s book is of no use”, and that Snyder “hasn’t really mastered the voluminous literature on Hitler’s Germany”, which “leads him into error in a number of places” regarding the politics of Nazi Germany

Mao did not cause the famine, China was a slave-feudal society where famine was a recurring feature due to underdeveloped agriculture and poor technology to cope with weather disasters. Famine was abolished under socialism during Mao’s time, just not overnight.

As for Robert Conquest, he’s a hack who includes Nazis killed as “victims of communism,” as well as non-births as deaths.

Wild Swans is a personal biography and anecdote, not an actual work of historical analysis.

Cambodia wasn’t socialist and the overwhelming majority of socialists condemn Pol Pot, so I don’t care to offer anything here.

All in all, you essentially have some of the worst of liberal academia combined with essentially historical fiction. That’s not a good basis for any historical analysis.

For the Soviet Union, I recommend the following works:

• This Soviet World (1936)

• Human Rights in the Soviet Union (1984)

• Blackshirts and Reds (1997)

• Stalin: History and Critique of a Black Legend (Published in English in 2023)

And for China, the following:

• China’s Millions (1965)

• The East is Still Red (2023)

• People’s Republic of China