Gross left Poland in 1969. Now 51, he was born and grew up in Warsaw - "one of my parents was Jewish, the other was not" - and started his university education there. In 1968, he became involved in the student demonstrations the Poles call "the March events."
"I was in prison for five months," he says.
What did he do?
"Nothing. They put in jail a lot of sort of visible students, student activists, if you wish. This was a crazy moment. The Communist regime was, on the one hand, launching a kind of anti-Semitic campaign, and on the other they had a lot of internal squabbles they wanted to solve. So ... it had nothing to do with anything."
One striking element of Gross' account in "Neighbors" is his belief that although the Germans sanctioned and approved the murders in Jedwabne - they were "undisputed bosses over life and death in Jedwabne" - their direct participation was minimal.
Szmul Wasersztajn testified that local bandits "from the Polish population" began an anti-Jewish pogrom as early as June 25, 1941, two days after the Germans arrived.
"I saw with my own eyes how these murderers killed," he said. "Jakub Kac they stoned to death with bricks. [Eliasz] Krawiecki they knifed then plucked his eyes and cut off his tongue. He suffered terribly for twelve hours before he gave up his soul."
Wasersztajn and several others tell of two distraught young mothers who drowned themselves and their newborn babies, "rather than fall into the hands of bandits."
After these horrendous events, a priest intervened to stop the pogrom, explaining that the German authorities "would take care of things themselves."
Wasersztajn says that on July 10, 1941, the Germans did in fact order that all "Jews be destroyed." The mayor and city council met with eight Gestapo men and agreed unanimously that all Jews must be killed.
"After this meeting the blood bath began," Wasersztajn testified.
"Local hooligans" took up their primitive weapons and chased all the Jews into the streets. They were apparently told they were going to clean the town square.
The Poles ordered young Jewish men to dismantle a huge, heavy statue of Lenin the Soviets had erected in the center of town, then carry it to a field and bury it.
"Then these Jews were butchered to death and thrown into the same hole," Wasersztajn said.
Several sources say that the youngest daughter of a teacher in the Jewish school was beheaded and her head kicked around like a soccer ball. Her picture is in Gross' book.
Finally the town was surrounded by mounted guards. The Jews were lined up and chased into a barn on the outskirts of town. The sick were carried in. Small children were tied together and pitch-forked onto the smoldering coals like so much brushwood.
Gross says Germans did little more than film the Poles killing their neighbors.
These narratives in his book grip the Polish nation.
"It's not surprising there is a debate," says Gross. "There are some who will say, `No, it never happened.' But there are these powerful voices who say, `Look, don't be crazy. This has happened and we must deal with it.' "
Even his critics concede that the "book is very much needed," as a writer for Rzeczpospolita put it. "It stirs our consciences, striking at the heroic image of the German occupation, in which there was generally no room for ... Polish participants in pogroms directed against the Jews."
Gross says, "It's clear that it's a liberating factor. People understand that to tell the truth about one's own past is simply necessary. Because otherwise you just sit on a big lie."