In 1939, Helga Weiss was a young Jewish schoolgirl in Prague. Along with some 45,000 Jews living in the city, Helga's family endured the first wave of the Nazi invasion: her father was denied work; she was forbidden from attending regular school. As Helga witnessed the increasing Nazi brutality, she began documenting her experiences in a diary.

In 1941, Helga and her parents were sent to the concentration camp of Terezin. There, Helga continued to write with astonishing insight about her daily life: the squalid living quarters, the cruel rationing of food, and the executions--as well as...