Yale University’s Cambodian Genocide Program’s website is the single best electronic source on the genocide. There are links to books, maps, testimonies, photographs, transcriptions of phone conversations between Nixon and Kissinger, detailed bibliographies of hundreds of books, etc.
This website was created by the Dith Pran Holocaust Awareness Project. Pran, a Cambodian journalist who worked with New York Times reporter Sydney Schanberg until the fall of Phnom Penh, spent nearly four years in forced-labor camps during the genocide. He devoted most of his life to increasing the world’s awareness about the Cambodian tragedy.
Hinton, Alexander Laban, Why did they kill? Cambodia in the Shadow of Genocide, University of California Press, 2005. This is one of the first anthropological analyses of the origins of genocide. Based on years of investigative work in Cambodia, Hinton finds parallels between the Khmer Rouge and the Nazi regimes.
Kiernan, Ben, The Pol Pot regime : race, power, and genocide in Cambodia under the Khmer Rouge, 1975-79, Yale University Press, 1996. The first definitive account of the four-year reign of terror, Kiernan depicts the horrific nature of the Pol Pot regime.
Power, Samantha, A Problem from Hell: America and the Age of Genocide, Basic Books, 2002. This outstanding book, a Pulitzer-Prize-winning examination of genocides throughout the 20th century, is an indictment of the lack of political will in the United States to prevent or stop genocide. Chapter 6 of this book (p. 87-154) discusses Cambodia.
Pran,Dith, compiler, and Kim DePaul, editor, Children of Cambodia's Killing Fields: Memoirs by Survivors, 1997. These are the stories of nearly thirty people who lived through the genocide as children.
Ung, Loung, First They Killed my Father: A Daughter of Cambodia Remembers, is a chilling autobiography of the author’s childhood during the violence of the Pol Pot regime. This highly-accessible book would be appropriate for high school or college students.
Weitz, Eric D., A Century of Genocide : Utopias of Race and Nation,Princeton University Press, 2003. Weitz, Chair of the History Department at the University of Minnesota, investigates four genocides: the Soviet Union under Stalin, Nazi Germany, Cambodia, and the former Yugoslavia and examines the dangerous mix of extreme nationalism and racial ideologies.
The Killing Fields, 1984, directed by Roland Joffe, starring Sam Waterston and Dr Haing S. Ngor. Based on The Death and Life of Dith Pran by Sydney H. Schanberg, this film, which won three Academy Awards, portrays the genocide through Cambodian photographer Dith Pran and New York Times reporter Schanberg as they cover the crisis, Pran’s subsequent incarceration in a forced-labor camp, and Pran’s eventual freedom.
For details about infrastructure, government, population, and the economy, the CIA Factbook has current information at https://www.cia.gov/library/publications/the-world-factbook/geos/cb.html