From the moment he read Mein Kampf, in 1925, Roman Vishniac took Hitler at his word. "Everybody said, 'He is an anti-Semite only until he comes to power,' " Vishniac recalls." 'Afterward, he won't need to be an anti-Semite. He will not murder any Jews.' I knew the danger was very serious, but nobody believed me." So, determined to record the age-old city and shtetl life of his people before it was snuffed out, Vishniac repeatedly trekked across Eastern Europe between 1934 and 1939. To blend in, he posed as a vagabond peddler. To avoid arrest by police as a spy—and because strict Orthodox Jews took the Torah's prohibition of graven images as a ban on having their pictures taken—Vishniac rigged his bulky Rolleiflex inside a capacious coat, the lens peeking through a buttonhole and the shutter cable fed through his sleeve to his right hand. In a scarf, he says, he concealed a small Leica. Vishniac had been taking pictures since his youth in Russia. The son of a wealthy family from a town near St. Petersburg, he became a biology professor and earned a medical degree before emigrating with his family to Latvia and then Berlin after the Russian Revolution. Surviving 11 arrests in his journeys as a photographer, Vishniac brought some pictures to the U.S. in 1941, hiding the rest in France. Of 16,000 negatives, he was later able to recover only 2,000. A few of his ghetto images became famous, but only with the recent publication of 180 prints in A Vanished World (Farrar, Straus & Giroux, $65) has his achievement been widely recognized. For Vishniac, who lives in New York with his wife, Edith, the pleasure is mixed with pain. "I lost 101 members of my family [in the Holocaust]," he says. "When people ask me about it, it's very difficult. I don't know where to start, because I know too much."