We all have learned it: The Holocaust lasted four years (1941-1945), took place in thousands of locations across an entire continent (Europe), and involved thousands of perpetrators and millions of victims. But when it comes to details, most of us flounder. Many websites can help us to learn more, and even a few encyclopedias. Leading among them is the four-volume encyclopedia published by Israel's Yad Vashem Holocaust Remembrance Center: The Encyclopedia of the Holocaust (1990). For every significant crime scene of the Holocaust, it presents a condensed narrative. However, it contains little if any information on what evidence this narrative is based on, and how this narrative has changed over time. While their encyclopedia contains many biographies of heroes, martyrs and villains, it contains not a single entry about witnesses and their stories, even though Yad Vashem insists that these stories are the foundation of our knowledge. We all know that, when a murder is committed, the murder weapon and the traces the murderers left behind are of crucial importance. Yet Yad Vashem's encyclopedia has no entries explaining scientific findings on these matters - not one. This is where the present encyclopedia steps in. It not only summarizes and explains the many pieces that make up the larger Holocaust picture, but it also reveals the evidence we have that confirms or contradicts certain notions. Nearly 300 entries present the essence of important witness accounts. They are all subjected to source criticism, which is the most important tool that a historian has. This enables the reader to choose which claim to believe, and which not. For all major Holocaust crime scenes, entries report about the sometimes-conflicting claims made about them. You learn how our knowledge has changed over time, and what evidence we have today that shores up the currently valid narrative of places such as Auschwitz, Belzec, Sobibór, Treblinka, Dachau and Bergen-Belsen, to name only a few. Several entries discuss the various tools and mechanisms reported by witnesses to have been used for the mass murders, and how the traces of the crimes were reportedly erased, if at all. Numerous other entries discuss toxicological issues surrounding the various lethal gases claimed to have been used. This encyclopedia also has multiple entries on some more-or-less common claims about aspects of the Holocaust, including a list of "Who said it?" This enables the reader to quickly find sources for the