Mr. Mueller is an American writer who lives in Italy. And not just anywhere in Italy but, his dust flap reveals, in a description that’s the prose equivalent of Corinthian leather upholstery, “in a medieval stone farmhouse surrounded by olive groves in the Ligurian countryside outside of Genoa.”

“Extra Virginity” grew out of a cogent article titled “Slippery Business” that Mr. Mueller wrote about olive oil in 2007 for The New Yorker, and his book is filled with information mindful eaters will wish to have. In this regard “Extra Virginity” is another reminder of why subpar nonfiction is so much better than subpar fiction.

With nonfiction at least you can learn something.

The news Mr. Mueller brings about extra virgin olive oil — E.V.O.O., as Rachael Ray likes to put it — is alarming. The liquid that gets passed off as such in supermarkets and restaurants is often anything but. Shady dealers along the supply chain frequently adulterate olive oil with low-grade vegetable oils and add artificial colouring.

Mr. Mueller cites an Italian producer who suggests that 50 percent of the olive oil sold in America is, to some degree, fraudulent. The Food and Drug Administration considers this adulteration a low priority. Grody olive oil is not killing anyone. We’re talking about a first-world problem here. Caveat emptor.

“Extra Virginity” suggests consumers put a priority on purchasing fresh olive oil, and taste before they buy. The good stuff is peppery and alive and, sipped neat, can make you cough. In the same way that many Americans have never tasted real maple syrup, not believing Aunt Jemima would do them wrong, many have no idea olive oil can be anything but a urine-coloured and musty butter substitute.

Mr. Mueller spends time with olive growers, with chemists, with cooks and with crooks. His history lessons are never less than interesting. He explains how olive oil was a driving force of life in the Mediterranean, a source of wealth and power. “A jug of olive oil on the dinner table,” he writes, “marked the triumph of Roman cuisine over barbarian beer and lard.”

The Greeks anointed their athletes with olive oil, which could be rather sexy. Mr. Mueller quotes Tom Scanlon, a classics professor at the University of California, Riverside, who says: “The oil on a gleaming, tanned, healthy body was a literally ‘flashy’ adornment. Oil heightened the body’s erotic charge, and encouraged male same-sex desire and pederasty, first in Sparta, then throughout the Greek world.”

Thomas Jefferson was among the first Americans to champion olive oil. He saw to it, Mr. Mueller writes, “that an olive branch, heavy with fruit, was placed in the talons of the eagle on the Great Seal of the United States.” Mario Puzo, in “The Godfather,” modeled Vito Corleone after a criminal olive oil boss named Joseph Profaci. Puzo even gave Corleone his own olive oil business, Genco Pura, as a front company.

For all its provocative bits Mr. Mueller’s book feels unctuous — oil coated — right from the start. It is packed with so many heroic artisans and sentimental peasants that it feels like a dinner theater production of “Fiddler on the Roof” or a canvas by Thomas Kinkade, the “painter of light.”

One man here has a “hint of wonder in his voice.” Another “laughed, high-pitched and merrily.” A woman has “almond-shaped eyes that seem to look straight into your soul.” This same woman has “a twinkle in her eye.” Throughout, it is as if we are reading about elves.

Olive oil brings out Mr. Mueller’s inner Windham Hill pianist. Olive oil reveals, he suggests, people’s “secret passions and dreams.” He speaks of its “sacred and mythic dimensions.” He writes about one producer: “Alissa Mattei is another person olive oil has touched, bringing out her inner contradictions.”

Mr. Mueller uses the words “wondrous” and “wondrously” in back-to-back sentences. A misdemeanor, but a telling one. When he inhales the scent of fresh oil, he reports that he has “aromas and aromatics dancing like angels in my nose.”

There’s a second funny moment in “Extra Virginity” when a Swiss agronomist explains, succinctly, what great olive oil will make a person do. It will make you, he says, “get down on your knees” like a Baptist preacher and shout out a word that’s not printable in a family newspaper.

That hollered obscenity reminds you that where there’s a flask of olive oil, you also pray to find some vinegar.