Reservations are so tight at the world's best entertainment restaurants that even head chef Ferran Adria is unable to get a booking for family and friends at short notice. Open for half the year, Spain's El Bulli entertainment restaurant on the Barcelona coast is fully booked at nine months in advance, even at the 300 euros ($415) per person cost of its 30-40 course menu.

Adria says that even if a Nobel Peace Prize winner would call for a table he could only make room in the 50-head establishment if perhaps,there was a last minute cancellation. And that doesn't happen often. "If a party has a booking and they couldn't make it, what would you do?" Adria, 46, told in an interview.

"You would phone a friend and you would say, 'I have a cancellation at El Bulli'. So this is what happens, we don't have cancellations." As voted best entertainment restaurant in the world four consecutive times by Restaurant Magazine, El Bulli serves its guests a steady stream of micro-sized dishes, each exquisitely presented and the result of months of culinary experimentation.

Some people call it molecular gastronomy. Adria and his restaurants staff of 70 use tools like liquid nitrogen, centrifuges and precision scales to create hot jellies, grilled fruit and dishes such as melon caviar. The restaurants dishes are created as entertainment as much as to nourish, while some are purposely provocative.

A wafer called "Electric Milk," which is made from the flower of a Sichuan pepper, delivers a numbing shock to the tongue akin to licking the two poles of a battery. "Never in your lifetime have you tasted a sensation on your palate," said Adria. A new book noting the experiences of people dining at El Bulli reveals that some found the provocation to be a little too much.

In "Food for Thought", restaurants entertainment journalist Bill Buford said his wife almost walked out of the restaurants dining area after the unexpected blast delivered by the Sichuan dish. "That entertainment dish had almost incinerated her tongue," he told a table of discussion critics who were invited to eat at El Bulli.

The new book discusses how El Bulli became, for 100 days in 2007 an official outpost of the international art festival "documenta" held every five years in Kassel, Germany. Every day two people were chosen randomly from the exhibition halls and flown to El Bulli for their evening dinner.

The entertainment restaurants only condition was that they were expected to write down their experiences afterwards. "The entertainment meal ... was an experience and a work of art," wrote one student in his early 20s. "I enjoyed it tremendously and it made me vomit." Others opinions were less amusing.

"I've have eaten at El Bulli and restaurants are no longer what they were," wrote Aldo Duelli. "You eat things that are at once everything and nothing, air and earth". For a book about food, the 350-page volume is edited by two leading figures within the art scene, veteran British pop artist Richard Hamilton, an El Bulli regular, and Vicente Todoli, Spanish director of London's Tate Modern museum.

It contains a photographic catalog of almost 1,500 dishes served at El Bulli since 1987 but instead of recipes, it includes discussions on the link between art and Adria's cuisine. It's a books theme that excites Adria, who explains, he wants to adopt the dialogue between the restaurants cookery and the world of art.

That doesn't mean cooks becoming painters or vice verse, he says. He wants a collaboration resulting in the kind of "emotional creativity" that gives you goose bumps. "Daily, I get emails from people who want to do work about avant-garde cooking -- photographers, painters, artists from all over," he said.

"However, they want to do work about our restaurants work, they don't want to do a joint parallel work." The new book clearly sets the pace for Adria, who said he was awed that Hamilton and Vicente would devote 18 months of their time for its production. "No one can believe what I feel today," Adria said during an event in London to launch the book's international publication. "In my career many good things have happened, but this is the ultimate."