I don’t usually read horror, but this one is a page-turner. And, unfortunately, true. The protagonist is a Slovakian Jewish teen named Walter Rosenberg, later known as Rudolf Vrba. First imprisoned during WWII as a 17-year-old, he manages to escape from at least two detention camps before being deported to Auschwitz in 1942.

From his earlier escapes, Walter understands two contradictory things: trust no one, and escape is only possible with help. The inhumane actions of his captors—and the randomness of their cruelties—is a psychological and physical nightmare. Not only Jews are imprisoned, and the criminal detainees work with the Nazis and impose their own versions of torture.

Walter is both clever and gifted with a prodigious memory. He uses it to mentally record the genocide occurring at Auschwitz-Birkenau: trainloads of Jews from around Europe, many led directly to the gas chamber/crematorium. He memorizes the shipments, where they were from, the tattoo sequences given to those sent to the camps, and the approximate numbers gassed.

Some of Walter’s lucky breaks read as incredibly improbable, but the proof is in the fact of his survival over a nearly two-year incarceration, during which hundreds of thousands died of starvation, slave-labor, and outright murder. During that time, he received tutoring from a Russian prisoner-of-war on how to escape. (It helped that Walter had a facility for languages as well.)

As spring of 1944 approaches, he learns that Hungarian Jews, who had largely avoided deportation up to then, were targeted for mass removal to the Auschwitz killing machine. He vows to warn them, believing that the allies were unaware of what was transpiring in Poland.

Along with one companion, he became the first Jew to escape from Auschwitz. Their harrowing journey finds them back in Slovakia where they report on the genocide to the Jewish resistance. Their report is known as the Vrba-Wetzler report. To Walter’s fury, the document does not include the important warning to the Hungarians.

Vrba—the name the resistance gave him for protection—wrote an autobiography. Freedland supplemented that work by interviewing people who knew him, both at Auschwitz and in later life. He also investigated what happened when the Vrba-Wetzler report was distributed to allied powers: what the allies knew, and their responses (or lack thereof) to the information about genocide.

It was only late in life that Vrba came to understand the difference between information and knowledge. Many of the Hungarian Jews deported in 1944 had been informed what would happen to them upon deportation, but they simply could not believe it to be true. They went off like lambs to slaughter, to Vrba’s great frustration.

Therein lies another lesson in the story: how painful it can be when people do not behave the way we wish they would. Unsolicited advice is often unheeded advice.