Man, oh Manischewitz, what a wine,” croons Sammy Davis, Jr. as he sings the praises of a kosher Malaga. Meanwhile Hebrew National, a manufacturer of kosher hot dogs, insists that its product “answers to a higher authority.” Is it a coincidence that two of the most catchy and inventive advertising slogans of all time touted the virtues of kosher foodstuffs? Sue Fishkoff doesn’t think so. “Kosher food and the kosher food system started out as Jewish, and like other immigrant food traditions, have become American,” she writes in her informative and richly researched book, which details how kashruth, the rigorous ancient system of Jewish dietary laws, has become a thoroughly American phenomenon.

In the manner of its production and distribution, and certainly its promotion, kosher food now owes as much to the conventions of modern America and the profit margins of big business as it does to the strictures of Leviticus, where the laws of kashruth—the separation of milk and meat dishes; the categorization of foods as acceptable (poultry and beef) or forbidden (shellfish, pork products)—are detailed. How that happened is the subject of her book, which offers a lively portrait of what it means to keep kosher in the twenty-first century.

Fishkoff’s account, which takes the form of a series of vignettes, covers a lot of ground, moving swiftly from suburban supermarkets and chemical laboratories to giant abattoirs, from the inside of a central New Jersey catering hall and the glorious vineyards of Napa Valley into the heartland of America—Postville, Iowa, where Agriprocessors, once the nation’s largest producer of kosher meat, held sway. Merrily de-mystifying along the way, it introduces readers to a wide array of people for whom kashruth is as much a way of life as it is a business or the stuff of a peppy jingle. We meet up with young foodies who make their very own kosher pastrami, and with the members of the Deli Maven club, a group of middle-aged men, expats from the East Coast, who meet monthly at a Berkeley, California, ‘kosher-style’ eatery to shoot the breeze and chow down on a corned beef sandwich. We encounter shochtim, or ritual slaughterers, who guard the secret of their special knives as if they were samurai swords, and with newfangled entrepreneurs like the folks behind 888-Go-Kosher who, armed with steel wool, kitchen cleansers and blowtorches, “help people go kosher from zero.”

Not everyone, of course, is a proud member of the “kosher nation.” Some of the characters whom Fishkoff befriends abjure kashruth, dismissing it as an “exercise in neuroses.” Others, like the members of classically Reform Jewish congregations, are somewhat less extreme in their characterization but give the dietary laws a cold shoulder all the same. “Kosher was fine five thousand years ago, but in the modern day I don’t see any purpose to it,” explains a Reform Jew from Colorado Springs for whom not keeping kosher is a family tradition that dates as far back as the 1880s. And still other American Jews, many of them in their twenties, would like to expand the meaning of ‘kosher’ to encompass morality as well as gastronomy. Profoundly disturbed by the unethical labor practices of Agriprocessors, whose workers, many of them illegal immigrants, were badly exploited, a new generation of observant Jews insists that it’s not enough to keep kosher; one’s behavior has to be kosher, too.

Most of those who inhabit these pages care a great deal about observing the Jewish dietary laws—so much so that they fret about the presence of decidedly unkosher microscopic critters in their drinking water and the little white bugs that infest fruits such as strawberries and vegetables such as broccoli. Some extremely observant Jewish communities like that of Lakewood, New Jersey, even ban the consumption of strawberries altogether, lest its members inadvertently violate the laws of kashruth.

Tempting as it might be to roll one’s eyes at the lengths to which some people go to honor the dietary laws, Fishkoff adopts a hands-off policy instead. She lets the material speak for itself, accumulating details and anecdotes instead of editorializing or issuing pronouncements. Sensitive to the ways in which kashruth is at once a hoary ritual practice and a modern-day business, a spiritual pursuit and an earth-bound enterprise, she has us see the many internal contradictions that keep the system spinning. To her credit, Fishkoff documents these tensions instead of erasing them, and as a result they emerge with full force, and on their own terms, to endow her narrative with bite and backbone.

One of her most striking findings is that as more kosher food products become available in the American marketplace, the more they become invisible. Once upon a time, kashruth rendered its practitioners and their palate distinctive and apart, the quintessence of otherness. To keep kosher was an exercise in restraint, abnegation, and culinary austerity; to keep kosher was to be out of step with everyone else. This is no longer the case. These days, kosher-keeping consumers pretty much eat the same things as their non-kosher counterparts. “Look, kosher organic cereal! Look, Belgian chocolates!,” trills Yakov Yarmove, who is responsible for stocking the shelves of the nation’s leading supermarkets with kosher products. Even Oreo cookies, once the forbidden food par excellence, is now under rabbinical supervision. Some kosher-keeping Jews might wonder what is lost and what is gained when little in the contemporary kosher diet is off limits. It is a good question, but for the most part it goes unanswered. The majority of kosher-keeping Jews delight in having their Oreos and eating them, too.

What makes Oreos and cereal and chocolates kosher is technology, and therein lies a fascinating tale of how the instruments of modernity often enlarge rather than diminish the parameters of religious experience in the twenty-first century. If there is a central character in Fishkoff’s heavily populated account, it is not the businessmen who flog kosher food, the advertisers who promote it, the ritual specialists who kasher meat, the rabbis who encourage its observance or the housewives who keep a kosher kitchen, but the scientists—the chemists and microbiologists—who call the shots. When it comes to determining whether or not something is kosher, Jewish law and Jewish folk practice now play second fiddle to online databases and microscopes, chemistry and microbiology. Years ago, you would take your chicken to your local rabbi to ascertain whether or not it was ritually permissible; today, it is inspected and duly certified by the lab before it even reaches the market.

Those who keep kosher in contemporary America are mindful of the concatenation of science and tradition that undergirds the rituals of their daily life. But, as this book reminds us, they are more mindful still of answering to an even higher authority.

Jenna Weissman Joselit is the Charles E. Smith Professor of Judaic Studies and Professor of History at The George Washington University.