This book by Professor Philippe Sands is a rare achievement that should be read by all who profess interest in international relations or international law. It explores the origins of ‘crimes against humanity’ and ‘genocide’ as foundational concepts of the international legal order post–World War II. The author weaves together the life stories of Hersh Lauterpacht and Rafael Lemkin, international lawyers who made decisive contributions to the inclusion of the two concepts in the 1945 Statute of the Nuremberg Tribunal and the 1948 Genocide Convention respectively. He traces their formation back to law studies in the Ukrainian city of Lviv, contrasting their lives with that of their contemporary, Hans Frank, governor of Nazi-occupied Poland, including Lviv. All three played roles in the Nuremberg trial in 1946: Frank as one of the defendants, Lauterpacht as a leading legal adviser to British prosecutors, and Lemkin as an independent lawyer seeking to have the Tribunal acknowledge an international crime of genocide. The book is based on comprehensive factual research and uncovers fascinating connections. The author constructs a tension between Lauterpacht’s promotion of the term crimes against humanity and concern that international law should protect the individual directly, and Lemkin’s preoccupation that international law must protect groups against genocide. The very end of the book seems to concede that the tension is deployed largely for dramatic effect – the author knows that crimes against humanity also protect group interests. Since ‘Historical Origins of International Criminal Law: Volume 3’ was published in 2015, we have also known that the term ‘crimes against humanity’ was used as early as 1861, 36 years before Lauterpacht was born and 78 years before the Nazi invasion of Poland.