This is not light reading.
An extensive look at the violence and mass murder of Communism. The Soviet Union gets the largest chunk, followed by China, but there's more. On Eastern Europe. On North Korea. On Vietnam, Laos, Camobia. On Latin America and Africa and Afghanistan.
Sometimes it turns into lists of victims and the particular, not much varying detail of how they ended up dead, but a lot covers the movements, the specific programs, the classes of victims, and means used to target, torture, and kill them.
Lenin was asked why the "The People's Commissariat on Justice", when "The People's Commissariat on Social Extermination" was more truthful. Lenin wished they could name it that honestly, but it's not possible.
The Cultural Revolution changed the name of so many shops in Shanghai to "The East is Red" that people had trouble finding their way around. (Not that that helped much.)
Pol Pot's immediate family members realized who he was only when they saw pictures of the leader -- and wisely kept their mouths shut. (Western spy agencies were in fact the first to realize he was the same as Saloth Sar, a Marxist guerrilla.