I judge books on science the same way I judge novels: I want them to be entertaining enough to carry on a plane, where I’ll be confined to a small space with little other entertainment. Mary Roach is one of the few science writers who passes that test. Her new book, “Gulp,” is an absolute delight. And if you’d like me to defend my position before you pack it for your next vacation, I will.

As with her previous books (“Stiff,” on cadavers, “Bonk,” on sex, and so on), “Gulp” explores a gross and engrossing subject of interest to us all. Everyone dies, everyone (well, almost everyone) has sex, and everyone digests. What makes her books so engaging, however, is not just their universality. She’s also a very good writer who understands that her job is, above all, to entertain. Every paragraph is a pleasure to read, even if that paragraph is about a partially decomposed gazelle entombed in the body of a python, or the fact that human hair can be used to make fake soy sauce.

In the wrong hands, a book on digestion would be rendered tedious by a need to cover every aspect of the subject to some degree. But Roach follows her interests, not a checklist. You won’t find much about ulcers, colon cancer, general nutrition or dental hygiene. You also won’t be forced to wade through long introductory sections explaining basic science, a trap that writers of a more scholarly bent often fall into when they write about their area of expertise for a general audience.

Instead you will learn, in a chapter called “I’m All Stopped Up,” how Elvis actually died. You’ll find out how competitive eaters put all those hot dogs away. And you will love the strange story of surgeon William Beaumont and his patient Alexis St. Martin, who, in 1822, was left with a permanent hole in his gut after surgery, through which Dr. Beaumont inserted all manner of digestible and non-digestible matter to find out what happened to it. Roach’s habit of weaving between arcane old experiments and futuristic science works particularly well here, as she draws a straight line from our weird, early history in medicine and biology to the present day.

What’s amazing is that Roach manages to follow her wide-ranging interests without leaving the narrative in shambles. Fortunately, the subject matter itself gives the book its structure — she begins at the mouth and works her way to, well, the other end of the digestive tract — and along the way, she populates the book with interesting, likable characters. The scientists themselves are Roach’s true subject. She writes not about a field of science, but of the day-to-day work that scientists do.

‘Gulp: Adventures on the Alimentary Canal’ by Mary Roach (W. W. Norton & Company)

And this is why I think you should read this book. Roach is interested in the act of doing science. She is curious about curiosity. In fact, I can’t think of another modern writer, or anyone from a previous era, who has so thoroughly — and so engagingly — written about the way scientists go about their work.

Consider, for instance, ecologist Richard Tracy, who is skeptical about reports that a darkling beetle larva, called a superworm, can actually survive in the gut of a bullfrog once it’s been swallowed. Such Jonah-and-the-whale stories circulate in the amphibian community, with biologists swearing that they’ve seen a mealworm or superworm chew its way out of its captor’s stomach. Tracy isn’t sure it’s possible, so he decides to conduct an experiment. “He calls up colleagues and acquaintances and tells them what he’s fixing to do,” Roach writes, “and they jump on board with offers to help.” Someone contributes a bullfrog, someone else has an endoscope, and a veterinarian offers to be the anesthesiologist.

It’s this sort of congenial, roll-up-the-sleeves approach to science that would make anyone want to take up a career as a biologist or a chemist. In Roach’s world, scientists don’t sit in meetings or apply for grants or grade papers. They drop a superworm down the throat of a mostly-sedated bullfrog, then dive in with a camera to see what happens to the creature once it’s in the gut. (It lives for a while but doesn’t seem able to gnaw its way to freedom.)

These experiments have all the elements of a great story — suspense, drama, conflict, comedy and tragedy. And Roach knows how to handle those elements and keep the narrative moving along.

The more squeamish might be reluctant to choose a book on digestion and its consequences for your next beach read, but Roach declares up front that she exercised restraint. Yes, there is a chapter or two on flatulence, and yes, there is a chart illustrating seven types of feces, but you’ll get through it. Her firsthand account of a fecal transplant — transferring fecal matter from a healthy donor to a sick patient to restore beneficial bacteria in the intestine — is not at all gross. In fact, it turns into a thought-provoking commentary on modern medicine. A patient suffering such serious colitis that he had developed internal abscesses and had to be fed intravenously experienced a full recovery two days after this simple and sensible treatment. (Don’t try this at home, by the way: Donors have to be screened for disease and parasites.)

Most of all, though, you’ll come away from this well-researched book with enough weird digestive trivia to make you the most interesting guest at a certain kind of cocktail party. I’ve explained to dozens of people how the enzymes in saliva prevent us from catching a cold when we drink after an infected person, and I try to introduce into every conversation the fact that dry pet food would taste like cardboard if not for the flavoring sprayed on the outside of the pellets. Such bite-size nuggets of alimentary trivia make this book easily digestible and, dare I say, delicious. Go ahead and put this one in your carry-on. You won’t regret it.


Amy Stewart is the author of “The Drunken Botanist: The Plants That Create the World’s Great Drinks.”


Adventures on the Alimentary Canal

By Mary Roach

Norton. 348 pp. $26.95