As a hidden child during World War II and an author of a memoir about my own experiences, I have attempted to read every book I’ve been able to find about the war—particularly those about the Holocaust. Thus, for the past couple of weeks, I’ve been asking myself: “How could I have possibly not known about Irena Sendler?” Now that I know her story, thanks to the immaculate research and wonderful writing of Tilar J. Mazzeo, I must conclude that Irena can easily be considered the greatest hero of the Second World War. After all, how many people can be credited with saving 2,500 precious lives?

Irena was a young Catholic social worker when the Germans invaded Poland and imprisoned Jews in the Warsaw ghetto. She was granted access to the ghetto—a walled town within a city—inside which horrific acts of inhumanity took place. Knowing that most of the inhabitants would either die of starvation or disease in the ghetto or be transported to the death camps of Treblinka or Auschwitz, Irena convinced parents to trust her with their children. Once the mothers and fathers made the painful decision, she and her network smuggled the kids out of the ghetto.

Sometimes very young children were medicated and hidden in boxes, suitcases, and even coffins. Once outside the ghetto, they were given new identities and placed in convents, orphanages, and with Polish families. In hopes that some of the parents would survive and return after the war, Irena kept a hidden record of the kids’ real names and where they were placed. She and her brave friends hid these records underground. They risked their lives every day, performing acts of humanity in the midst of cruelty and death.

Tilar J. Mazzeo’s book is not an easy read—the details of Nazi savagery she describes often are difficult to absorb. At the same time, I consider it one of the finest pieces of work I have read about the Holocaust. The combination of excellent narrative style and its subject—the heroic Irena Sendler—make this little-known story of the war a must read. I could not recommend it more highly.