“Did he have rags on his feet instead of shoes?” Mr. Rosenblat said he asked her.

She said yes and he told her, “That boy was me.”

In a telephone interview Sunday, Ms. Hurst, who sold the book to Berkley for less than $50,000, said she always believed the essential truth of Mr. Rosenblat’s tale until last week. “I believed the teller,” Ms. Hurst said. “He was in so many magazines and books and on ‘Oprah.’ It did not seem like it would not be true.” On Sunday, Ms. Hurst said that she was reviewing her legal options because “I’ve yet to see what kind of repercussions could come from this, and I was lied to.”

Ms. Hurst said that Mr. Rosenblat did provide some documentation, including a 1946 letter from a warden with the Jewish Children’s Community Committee for the Care of Children From the Camps that said Mr. Rosenblat had attended a technical school in London. Evidence of an organization with that name did not appear in Internet searches on Sunday.

Susanna Margolis, a New York-based ghost writer who polished Mr. Rosenblat’s manuscript, said she was surprised by his description of his first blind date with Ms. Radzicki. “I thought that was far-fetched.” she said. “But if somebody comes to you, as an agent and a publisher, and says, ‘This is my story,’ how do you check it other than to say, ‘Did this happen?’ ”

That so many would get taken in by Mr. Rosenblat’s inauthentic love story seems incredible given the number of fake memoirs that have come to light in the last few years. The Holocaust in particular has been fertile territory for fabricated personal histories: earlier this year, Misha Defonseca confessed that her memoir, “Misha: A Mémoire of the Holocaust Years,” about her childhood spent running from the Nazis and living with wolves, was not true.

A decade ago, a Swiss historian debunked Binjamin Wilkomirski’s 1996 memoir, “Fragments,” which described how he survived as a Latvian Jewish orphan in a Nazi concentration camp. It turns out the book was written by Bruno Doessekker, a Swiss man who spent the war in relative comfort in Switzerland. Mr. Rosenblat, at least, appears to have told the truth about being a prisoner in the Nazi concentration camps.

The primary sleuth in unmasking his fabrication of the apple story was Kenneth Waltzer, director of Jewish studies at Michigan State University. He has been working on a book on how 904 boys  including the Nobel Peace Prize winner Elie Wiesel  were saved from death by an underground rescue operation inside Buchenwald, and has interviewed hundreds of survivors, including boys from the ghetto at Piotrkow in Poland who were taken with the young Herman Rosenblat to the camp.