Are you thinking of what book to read before the year 2026 runs out? Well, you can try out The Great Big Book of Horrible Things, a popular history book written by Matthew White, that provides a ranking of the hundred worst atrocities of mankind based on the number of deaths.

White, a librarian at the federal courthouse in Richmond, Virginia, United States of America, wrote the book in 2011. 

He previously administered the Historical Atlas of the 20th Century on his own website, and became interested in the subject due to constant arguments in cyberspace about who was actually responsible for various atrocities throughout history. 

According to White, the Atlas has been used as source by many authors, including in 377 books and 183 scholarly articles.

The book was first published in hardcover by W. W. Norton & Company in November 2011. The paperback was published by W. W. Norton in May 2013 under the new title Atrocities: The 100 Deadliest Episodes in Human History. 

The British edition (Canongate Books, 20 October 2011) is entitled Atrocitology: Humanity's 100 Deadliest Achievements. It has been translated into Italian, Japanese, Portuguese, and Spanish.

The book chronologically lists the hundred atrocities. Some of these are the Khmer Rouge rule of Cambodia, An Lushan Rebellion, and World War II. The book's top-ranked events include World War II at number one, followed by the Mongol Conquests, Mao Zedong’s regime in China, famines in British India, and the fall of the Ming Dynasty. Lower-ranked examples on the list range from the Atlantic Slave Trade to the American Civil War and the Roman-Jewish Wars.

White's methodology for creating the list was gathering all available data on atrocities and attempting to discern consensus estimates for each one's death tolls. His focus is on armed conflict, with famine and disease relating to such conflict counting for the statistics, while natural disasters and economic events do not. 

White says that there is no atrocity for which the statistics can be agreed upon worldwide. One of White's conclusions is that no one system of government is obviously more murderous, and anarchy can be worst of all. He adds that governments do not kill people, rather people kill people. Another conclusion is that chaos is more deadly than tyranny.