A picture may be worth a thousand words, but the photograph taken in 1933 of a brown-skinned boy wearing a swastika in a schoolyard in Hamburg, Germany, does not begin to tell the story of the remarkable life of Hans J. Massaquoi. Mr. Massaquoi, former managing editor of Ebony magazine, has now told the story himself in his new book, Destined to Witness: Growing Up Black in Nazi Germany.