By Matthew Wells
BBC News, New York
Mrs and Mr Zagat are ready to face online competitors
It is the best selling book in New York every day of the year.
The modest maroon cover of the Zagat Survey has now become a familiar sight in 85 of the world's largest cities, incorporating the critical insights of almost 300,000 people.
Stories like that of Tim and Nina Zagats' rise, from personal hobby to business empire, have become familiar in the internet era.
But their simple concept was born before anyone knew what being "online" meant.
In the late 1970s, the couple began comparing views on restaurants in their native New York, with a few dozen friends.
As the 1980s beckoned, they created their Zagat Survey company, by inviting food lovers to review local eateries, awarding up to 30 points on a variety of criteria.
"Our voting is incredibly comprehensive," says Tim Zagat, sitting beside his wife.
"We probably have three to five people in every restaurant, at every meal, all year long.
"We cover 2,000 restaurants in New York."
There are about 31,000 New Yorkers who actively contribute to the Zagat Zeitgeist.
The internet means that ratings can be updated instantaneously now, and the Zagats plan to have a daily member-update service online by the end of this year.
Although the couple still resemble the genial, affluent, uptown lawyers that they once were, they are as much a part of the internet boom as the designer-clad, downtown hipsters, who trade in celebrity-stalking.
In 1999, they launched Zagat.com, creating an instant solution to the guide's biggest flaw - the fact that restaurants come and go in the city every day.
So even though it goes through up to seven updates as editions sell out through the year, the New York restaurant guide is invariably out-of-date before it even hits the shops.
Mr Zagat explains why their website is different from others out there in cyberspace.
The Zagat range is gradually being broadened
"We have a very disciplined surveying process," he says.
"Secondly, we don't want just anybody going in, and throwing their comments on the wall."
The Zagats have spent "millions" protecting the integrity of their aggregated customer reviews, making it as tamper-proof as possible.
As with any 40-year marriage, the couple - who share the chairmanship of the company, while Mr Zagat is chief executive - are comfortable interrupting each other brusquely when describing business strategies.
Mrs Zagat wanted to stress the liberating role of growing beyond the book, and onto the web.
"The Zagat published content that goes with our brand is something completely different from what you find on blogs and user-reviews on the net," she says.
"That information is where we start. That's the unwashed material.
"What we do is take that information, that we value tremendously - the voice of the public - and synthesize it."
There is plenty of free information on the Zagat site, but it costs $25 for a year's full subscription if you want to access the ratings and key list.
And the Zagats have managed to buck the trend and make their site profitable.
The surveys have grown way beyond food, covering spas, airlines, golf and music, to name but a few.
Mr Zagat is keen not to comment on company performance figures as they remain a private company, but to give an idea of the volume of business, the New York restaurant book sells around 650,000 copies per year.
The Zagats have recently added a Shanghai guide to their stable, and Beijing is coming out soon.
They plan to expand into India and ride the world's urban growth boom for as long as it lasts.
"The most important trend of the last 25 years is an on-going revolution in the internationalisation of food," says Mr Zagat.
They see their guides and the site as a leading manifestation of "consumer democracy" and they deny that the Zagats' venerability and upscale values means they are well behind the cutting edge.
"Our average age of surveyors for the nightlife guide is about 28," says Mr Zagat.
"The average age of all surveyors for restaurants, is about 38 or 39."
Mrs Zagat points out that the guides also try to cater for all strengths of spending power.
"We try to make sure that our guides are available to serve any economic range," she says. "That's why we have budget conscious places - best bangs for the buck - in the front of each guide."
Ready to compete
But it is not just their reputation as an icon of the comfortable middle-class consumer that leaves the Zagats vulnerable when compared with free internet guides like Citysearch.com.
A critical article published recently in SmartMoney magazine asserts that compared with the early years, the modern Zagat surveys are guilty of toning-down the criticism and inflating the points awarded.
When the journalist who wrote the story put it to Mr Zagat that since the 1983 guide came out, New York restaurants have gained 5 points on average, he reportedly stormed out of the interview, leaving his wife to state - convincingly perhaps - that quality has simply improved all-round in the last few decades of "foodie" culture.
The extra points, in other words - are well deserved.
The Zagats themselves do not take part in their own surveys, although they still enjoy New York restaurant life as much as ever.
There is no doubt that despite their homely image as the godfather and godmother of the consumer ratings industry, they are here to stay and ready to compete energetically, with whatever the fast-moving internet world throws up.