Since Mary’s mother was an American citizen, the family lived in a relatively privileged part of the ghetto, protected from many of the horrors that Mary recorded, partly in code, in a series of spiral notebooks. In July 1942, the family, along with other foreign citizens, was moved to Pawiak, the Warsaw prison from whose windows Mary watched as Jews were shot or rounded up for transport. In January 1943, the family was sent to Vittel, France, to an internment camp for British and American citizens, shown in several pages of photographs.

When Mary, her sister and her parents sailed to the United States in March 1944, they were part of an exchange for German prisoners of war. Almost immediately, they met S. L. Shneiderman, a journalist who helped Mary turn her diaries into a series of articles and then a book, published under the pen name Berg, a shortening of her family name, Wattenberg. (The original notebooks are not known to have survived.) A thick scrapbook of newspaper clippings and other material carefully records the book’s reception — The New Yorker called it “brave and inspiring” — and Mary’s various public appearances.

Alexandra Zapruder, the author of “Salvaged Pages: Young Writers’ Diaries of the Holocaust,” who has not seen the new material, said it could shed light not only on Ms. Berg’s life but also on the period when public memory of the Holocaust was still being formed.

“It’s interesting that there was someone who came along before Anne Frank but didn’t have that same lasting hold on the public imagination,” Ms. Zapruder said. (“Anne Frank: The Diary of a Young Girl” was published in English in 1952.)

In part, that’s because Ms. Berg resolutely distanced herself from her diary, a posture she maintained even as the Holocaust became a more prominent topic of public conversation.

A 1986 article in The New York Times about a stage version in Poland noted that Ms. Berg had “let it be known through friends that she does not wish to talk of her book or her memories.” When Susan Lee Pentlin, a professor at the University of Central Missouri, was preparing a new edition of the book in the 2000s, Ms. Berg brushed her off. “Mary told her to get a life; there were other things happening the world,” Floyd Pentlin, Ms. Pentlin’s widower, said in an interview. “She accused Susan and others of making money off the Holocaust.”