The book designed to explain the Muslim faith to Jews was published in May, the death threat came in June, and the author is now huddled out of sight in a safe house.
Jewish and Muslim groups, meanwhile, are left to ponder what can happen next to make the situation any worse.
The irony of the situation is rich: A book conceived by the American Jewish Committee (AJC) to advance Muslim-Jewish understanding may in fact end up exacerbating tension between the faiths.
A fatwa -- or religious edict -- was issued by a Muslim cleric to "shed the blood" of the author, Prof. Khalid Duran, but later was clarified as merely a call to investigate him.
Depending on the findings of the probe, though, Duran still could be declared fit for killing.
The AJC condemned the edict by Sheikh Abd-al-Mun'im Abu Zant, a leader in the militant Islamic Action Front, an opposition party in Jordan.
"In a free society, no one should tolerate the threat to kill an author," said David A. Harris, executive director of the AJC, which published Duran's book, "Children of Abraham: An Introduction to Islam for Jews," as well as its companion volume,"An Introduction to Judaism for Muslims. "
"All Americans, not least Muslims, should immediately speak out against this outrage and assault on democratic society," Harris said.
The other volume in the series, "Children of Abraham: An Introduction to Judaism for Muslims," was written by Reuven Firestone, a professor and rabbi at Hebrew Union College.
Firestone's book has not attracted much media attention, and is considered an innocuous primer on Judaism.
But Duran has been under scrutiny from the start. A leading analyst of Islam and politics, he has written six books and has taught at Temple University and American University, but also is something of a polarizing figure in the Muslim world.
The Washington-based Council of American Islamic Relations, which has voiced support for militant groups such as Hamas and Hezbollah, attacked Duran's book even before it was published.
Arab newspapers took up the issue, denouncing Duran for supposedly spreading "anti-Muslim propaganda."
The AJC called such attacks "nothing more than incitement and character assassination."
Although Duran's book was reviewed and approved by Islamic scholars before publication, and has been well received by trade publications, some have questioned his scholarship.
Hussein Ibish, communications director of the American-Arab Anti-Discrimination Committee, maintains that Duran is not a reputable scholar and calls his book "bizarre." But Ibish admits that he finds the incident troubling, and said it cannot help the already tense relations between Jewish and Muslim groups.
"Intolerance is spreading like wildfire on both sides," Ibish said.
Ibish believes the situation is symptomatic of the heightened tension around the violent conflict between Israelis and Palestinians. And, he says, it also illustrates how the American press notes the intolerance only on the Arab and Muslim side -- while allegedly ignoring what Ibish considers similar behavior from Israelis and Jews.
Duran reportedly has left his home in suburban Washington for a safe house with 24-hour private security. Attempts to contact him by telephone were met with a recording saying the number had been temporarily disconnected.
Despite the uproar, the AJC still believes the book can achieve its purpose of promoting coexistence. Duran's book will get into the hands of people who need it and will have a tremendous impact, predicted Shula Bahat, AJC's acting executive director.