During World War II, Rudolf Hoss ran the “most effective killing machine in human history, capable of murdering over four thousand people a day,” Thomas Harding writes in his compelling contribution to the vast, depressing and mesmerizing literature of the Holocaust. As commandant of Auschwitz, Hoss supervised the elimination of roughly 3 million people, mostly Jews. Interrogated after the war, he seemed matter-of-fact, almost apathetic about his crimes. “I am entirely normal,” he insisted.

Harding, a former documentary filmmaker and journalist who has written for the Guardian and the Financial Times, is a great-nephew of the Nazi-hunter Hanns Alexander, who captured Hoss in 1946. Told by his family not to ask questions about the war, the author learned about his great-uncle’s exploits only at his funeral in 2006. Harding, who had always regarded his great-uncle as “nice but unremarkable . . . a bit of a rogue and prankster,” set out to tell the tale of a mass murderer and his somewhat unlikely pursuer.

Hoss was, at least in the beginning, an ordinary thug, one of countless young bullies who donned brown shirts and saluted Adolf Hitler as the Nazis rose to power in the early 1930s. But he was well connected, a friend of Hitler’s SS chief, Heinrich Himmler, and he showed an early aptitude for running concentration camps. In 1940, Himmler told Hoss to build an especially large camp in an out-of-the-way town in Upper Silesia called Oswiecim by the Poles and Auschwitz by their German masters.

Hoss’s job was to eliminate Jews and other “untermenschen” (subhumans) as efficaciously as possible. Executions were found to have an emotional impact on the firing squads, causing excessive drinking and suicide rates. But one of Hoss’s aides discovered that a pesticide called Zyklon B could be used more impersonally, and soon Auschwitz was making its large contribution to the Final Solution. “Now my mind was at ease,” Hoss wrote in a postwar memoir.

The commandant did not spare himself from the ghastliness. Day and night, hour after hour, he stood amid the “dreadful, sinister stench,” he recalled. He looked through the peephole into the chamber and watched the inmates die. “I had to do all this because everyone looked to me,” he explained. He did not want to appear soft. To pacify the ones who were strong enough to be sent to the nearby slave-labor factory, Hoss organized an orchestra, made up of inmates who competed for seats, to play selections from “Rigoletto” and “Madama Butterfly.”

’Hanns and Rudolf: Hanns and Rudolf: The True Story of the German Jew Who Tracked Down and Caught the Kommandant of Auschwitz’ by Thomas Harding (Simon and Schuster)

Hoss was a family man, after a fashion. His wife, Hedwig, who lived in luxury on the far side of a garden wall in the camp, called Auschwitz “paradise. I want to live here till I die.” Hoss doted on his four children, though he cheated on his wife with an inmate, whom he impregnated (she was forced to have an abortion). In his memoir, written in a somewhat unconvincing effort to show that he “had a heart, and was not a wicked man,” he admitted to some personal cost. “I withdrew more and more into myself. I became unapproachable and visibly harder. My family suffered, particularly my wife, for I was often unbearable company.”

The man who captured Hoss was a German Jew. Hanns Alexander came from a highly assimilated and party-loving family that stayed in Berlin until it was almost too late, finally fleeing to Britain in 1936. Little Hanns and his twin brother, Paul, were for most of their indulgent childhoods oblivious to the anti-Semitic plague growing all around them. Their parents were cultured haute bourgeois; among their dinner guests were Albert Einstein and Marlene Dietrich. In 1939, Alexander joined the British army and served uneventfully until, in May 1945, he came upon the shocking scenes of stacked corpses at the newly liberated Belsen concentration camp. Carrying bodies to their graves, he was “gripped by a barely controllable rage.”Though he had no policy experience, no support and no clues, he became a self-appointed Nazi-hunter.

The once-spoiled and jolly boy learned how to be cruel in the cause of revenge. Tracking down Hedwig in an abandoned factory outside Berlin, he broke her silence by threatening to put her young son on a train to Siberia. She directed Alexander to the farm where Hoss was hiding under the assumed name of a dead sailor. When Hoss refused to identify himself or to hand over his wedding ring, Alexander threatened to cut off his ring finger. Hoss gave him the ring — with the names Rudolf and Hedwig inscribed inside the band. Alexander left the prisoner alone with some guards and a box of axe handles for 10 minutes. A doctor told him that if he did not cut the beating short, he would have only a corpse to bring back.

Alexander was nothing like the monster he pursued. But the desire for revenge filled him with a deep hatred he spent the rest of his life trying to conceal from his family.

The most moving twist in the story comes at the end, when the author visits the site where Hoss was hanged after being convicted of war crimes. Accompanying him, incredibly, is Hoss’s grandson, Rainer Hoss. Written with admirable restraint, “Hanns and Rudolf” lacks the haunting, lyrical grace of another recent Holocaust remembrance, Edmund de Waal’s “The Hare with Amber Eyes.” But it still fascinates and shocks.

Evan Thomas , the author of “Ike’s Bluff,” is writing a biography of Richard Nixon.


The True Story of the German Jew Who Tracked Down and Caught
the Kommandant of Auschwitz

By Thomas Harding

Simon & Schuster. 348 pp. $26