When David Sax set out to write a book on the death of the delicatessen, he already had the ending worked out: A world without pastrami on rye was at hand.

But after searching out deli meats and other eats across the country, and watching Manhattan’s Second Avenue Deli reopen last year to lines that stretched around the block, Sax retooled his thesis.

“People were lining up around the block for two weeks straight, to get in to eat at this deli that had been closed down two years before,” said Sax. “There was one guy who had taken a jar of Second Avenue Deli mustard and kept it in his freezer. He held it whenever he was worried the deli wouldn’t come back, held it tight like a little talisman.”

Sax’s book became “Save the Deli: In Search of Perfect Pastrami, Crusty Rye, and the Heart of the Jewish Delicatessen.” He will discuss it at Amherst’s Nosh Cafe on Nov. 19, as part of the ongoing Jewish Community Book Fair.

The demographics of Jewish migration, changing appetites and rising deli rent have caused many delicatessens to close, depriving populations of their smoked pastrami, corned beef and matzo ball soup, Sax said. But as the man with the Second Avenue mustard made clear, delicatessen speaks to the souls of its fans in a way baloney never will.

“That passion, that love for it, it made me realize that it’s never going to really go away,” Sax said in a phone interview. “But if we don’t fight to preserve it in people’s consciousness, the decline will continue.”

A native of Toronto and veteran journalist, Sax spent a year searching out the delicatessens of America and Europe before writing his book. He traces the birth and growth of the delicatessen from its roots in the Ashkenazi Jewish and German immigrants to New York City, to its American heyday in the 1950s and ’60s.

Today, Sax said, most of the country finds itself in a similar position to Buffalo, with delicatessen fans worrying about whether they’ll be able to get their favorite sandwiches.

“All the big cities have something, maybe one or two places,” said Sax. “There are certainly medium-sized cities that don’t have any.”

The Buffalo area has two standalone Jewish delis currently open, neither within city limits. In fact, both are on the same stretch of suburban Transit Road, about three miles apart. There’s Nosh Cafe (7900 Transit Road), where Sax will be speaking, and Jonny C’s (9350 Transit Road).

Before the New Year, Buffalo is expected to have a Jewish deli again, as Risa’s, formerly of Hertel Avenue, reopens downtown at 285 Delaware Ave.

Risa Paonessa, daughter of one of Buffalo’s deli families, said that she and her father Anthony Gengo talked about opening a downtown deli years ago, when he was the “pastrami king of Buffalo.”

Gengo’s Ralph’s Restaurant, later named Stumpy’s Deli, was down the street from Mastman’s kosher deli on Hertel Avenue, Paonessa said.

“It’s a warm atmosphere in the deli,” Paonessa said. “It was kind of like Cheers — we knew everybody’s name and what they ordered. Homey food, a homey feeling. People had it at home for a happy meal, and I just think it brings good feelings to people.”

Now that word has gotten out that Risa’s is reopening, people’s pastrami passions have been showing, Paonessa said. “We can’t go out without someone saying to us, ‘Where did you go? What’s happening?’ So it really is a wonderful response,” she said. “Even the people from Damon and Morey, the law firm that handled the lease, they’re just a block away—they can’t wait.”

No matter where he found a deli, Sax said, he found people carrying on a lifelong love affair with pickled meats and savory soups.

“There are people who have a passion for this food that you just don’t really see with other types of foods,” said Sax. “Deli lovers are fanatics, in the best sense of the word. These are people who can remember a sandwich they ate 40 years ago, to the detail, right down to the consistency of the bread, and how much it cost. It’s always about how much it cost.”

When Sax started searching for people to tell their delicatessen stories, he found delicatessen families to share their tales, and other expected fans, like actor-director Mel Brooks.

“I’ve been able to tap into this well of emotion that people have,” Sax said. “It is, in some ways, nostalgia, but in other ways a genuine, heartfelt yearning and love for a genuine culinary institution and culture.”

Others he found challenged the image of delicatessen as food for old Jewish guys. Mr. T, the chain-draped ex-bouncer who starred in “Rocky III” and “The A Team,” has been a fan of Junior’s delicatessen in Los Angeles since his movie star days.

“Anyone who says deli is bad for you: I pity the fool!” the actor says in the book. “A lot of people get caught up in health food, walk out, and get hit by a truck!”

It’s in L. A., amid the movie stars, that Sax comes up with his biggest surprise.

The deli capital of America is Tinseltown, Sax insists.

“I didn’t expect it to be a good deli town,” the author says, half-apologizing. “I expected it to be lousy. L. A. is the land of tofu and California fusion cuisine, low fat and fake breasts. I didn’t expect it to be great here, and within four meals I was just blown away.”

In Los Angeles, the delicatessen business seems to be alive, working its way into the local culture in a way Manhattan can no longer muster, Sax said.

“There’s a relevance to it,” Sax said. “New York deli is very much about nostalgia. It’s a Sunday afternoon thing. In L. A. it’s the here-and-now. People in L. A. go to delis every day, and that makes a difference in the quality and the flavor, and the way the delicatessens operate.”

Deli is spreading out into the culture in Los Angeles, not shrinking, Sax said. “Pastrami here is a condiment,” he said from his Hollywood hotel room. “They put pastrami on everything. It has really permeated deep into the culture of L. A.’s eating habits. It used to be that way in New York, but it’s not any more.”

As a peacemaking gesture, Sax offers this comparison: “L. A. is the Tel Aviv of deli, and New York is the Jerusalem, the spiritual birthplace that will always be the mecca,” he said. “But if you want the best of the here and now, welcome to Tel Aviv.”

Buffalo-area delis

Nosh Cafe: 7900 Transit Road, Amherst, 633-8417

Jonny C’s: 9350 Transit Road, Amherst, 688-8846

Opening by New Year’s: Risa’s: 285 Delaware Ave. Buffalo

Toronto-area delis

Caplansky’s: 12 Clinton St., Toronto, (416) 500-3852

Centre Street: 1136 Centre St., Thornhill, (905) 731-8037

Yitz’s: 346 Eglinton Ave. W., Toronto, (416) 487-4508