John Hersey was a master at both fiction and nonfiction writing. He wrote more than 20 books, including Hiroshima, a short but searing account of the effects of the atomic bomb as seen through the eyes of six survivors. He won the Pulitzer Prize in 1944 for his novel A Bell for Adano.

Mr. Hersey was also a teacher, serving as a professor at Yale University for nearly 20 years.

In 1987, at the age of 74, he merged these diverse talents in his bestselling book Blues, a most curious and beloved creation that turns 25 years old this year. Mr. Hersey died in 1993.

Blues is part fictional conceit and part factual account, telling the story of the bluefish, a fish Mr. Hersey loved and fished for all his life in the waters around Martha’s Vineyard. It is also an instructional manual of sorts. After reading Blues, you not only know how to catch them, but where to find them, which lures to use, how to fillet them, cook them 12 different ways, even their mating habits.

But back to the fictional conceit.

The book opens with a fisherman, named the Fisherman, coming in to dock in Vineyard Haven harbor after a day of fishing aboard his boat, Spray (also the name of Mr. Hersey’s real-life boat). On the dock a man, the Stranger, stands watching, “rooted to the shore like a tree.”

The Fisherman and the Stranger exchange pleasantries during which the Stranger admits he has never been fishing or on a boat at all. “I have been completely land-bound all my life,” he says. “I’ve lived in cities. When I travel here it’s by air; I’ve never even ridden the ferry from Woods Hole.”

When asked by the Fisherman what he has been doing coming down to the docks each day, the Stranger replies: “There seems to be an empty place in my psyche, where a feel for the sea should be, and I guess I’ve been wishing I could fill it.”

And with that the book is underway. Mr. Hersey the teacher has created the perfect pupil for his book. The student is completely ignorant, a blank slate with regard to the subject of fishing for blues and the ocean itself. The student also carries with him a mild skepticism but he is curious and very quickly completely hooked and under his teacher’s spell.

The rest of the book is comprised of 12 chapters, or rather 12 fishing trips, during the course of one season, from June 10 to Oct. 28, with a break for the August spawning. During these trips, mostly to Middle Ground, the stranger plays the part of a teacher’s pet, asking the type of questions a professor could only dream about, and listening with rapt attention as the Fisherman discusses lures, bait, tides, feeding habits and the mystery and plight of the ocean and its inhabitants. At the end of each trip the two take their catch back to the Fisherman’s house, where Barbara, (the name of Mr. Hersey’s real wife) awaits. They cook up the bluefish, a different recipe provided each time, and then the chapter ends with a poem by John Donne, Elizabeth Bishop, Robert Penn Warren or even Homer that captures their experience during that day.

If this sounds didactic or boring, a monotone treatise of how-to’s and what-not-to-do’s, it’s important to remember that Mr. Hersey is a master at his craft, which his many books attest to. And although his work as a professor took place before the time of podcasts and so cannot be experienced today, it is clear he must have been a wonder in the classroom. Consider how he praises his pupil after the Stranger finally catches his first fish.

“Maybe when you were born your mother threw your umbilical cord into the sea, the way Fijian women used to do, to make their sons good fisherman.”

“I doubt it. We lived in Ohio,” the Stranger replies.

Mr. Hersey also employs a unique braking system when he realizes he is about to lose the Stranger (and the reader) after setting the hook on some subject other than fishing, be it the effects of nuclear waste on the seabed floor or the microscopic wonders of life found in each drop of seawater, which he examines with a biologist in Woods Hole.

Author John Hersey in 1988. — Alison Shaw

“Soon, as if unexpectedly seeing the faces of friends in a rush-hour Lexington Avenue subway car, I recognized in this pulsating little drip of the ocean some individuals I’d read about, seen pictures of. Their forms were as various, it seemed, as the patterns of snowflakes.” He goes on to list all the life forms he sees in this drop, from copepods to radiolaria, flagellates and nauplius, and also the harsh realities of the natural world, even at this infinitesimal level.

And then, just when you begin wondering if you were duped and that the title of the book has no bearing on the contents within, the Fisherman interrupts his lecture with a cry of “Fish on!” and he or the Stranger is back to the business at hand, reeling in a bluefish for dinner.

If only every professor had employed a similar tactic we may all have never left school.

One of the ongoing refrains throughout the book, uttered by both the Fisherman and the Stranger, is that “fishing is complicated.” At times they are talking about the difficulties of finding and landing a fish. More often, though, they are talking about the killing of a wild creature they have come to love and respect.

“It’s always so peaceful, coming back in,” the Fisherman says. “We’ve done our work. The sea has done its work in us. The bay welcomes us. See how East Chop glows in this light.”

“But that thumping in the box,” replies the Stranger. “Isn’t that death coming on?”

“Yes. I told you, fishing is complicated. It dies for our living . . . .”

Fishing is also complicated because spending time on the water allows the fisherman to see, firsthand, the effects of pollution on our natural resources.

“This mischievous trickle into the ocean from bathrooms and kitchens and washing machines is of course nothing compared to the obscene excretion into our rivers and bays of the toxic wastes of industrial plants.”

In Mr. Hersey’s hands these are not merely opportunities to complain but rather a chance to study and illuminate the science of these adverse effects, from the growth of algae to the loss of spawning grounds. It also allows him to travel deeper into the very conscience, or lack thereof, of man.

“Just as those who decided to drop the bombs on Hiroshima and Nagasaki gave no thought to their long-term radiation effects on human victims, so those who later made decisions about testing nuclear weapons over the seas, and about flushing wastes from nuclear power plants did so with little or no thought of the subtle long-term effects of their actions on the delicate balances of oceanic life.”

Yes, fishing is complicated when a trip to Middle Ground on a beautiful summer day leads to thoughts of Hiroshima. And yet, for Mr. Hersey, who traveled to Hiroshima just days after the bomb exploded to report on the after-effects, one can imagine August 6 , 1945 was always on his mind. Mr. Hersey’s account, told through the eyes of six survivors, some of whom lived within just a few hundred yards of the blast and had somehow lived while over 100,000 of their fellow civilians died, was first published in the New Yorker magazine on August 31, 1946. It took up the entire magazine, no other stories or events were included in that edition.

“Fish on!”

Yes, it is a handy technique, and time to turn back to the main subject at hand. For while fishing is complicated, especially in the capable hands of Mr. Hersey, the majority of Blues revels in the sheer joy of having one on the line.

“Will I really know when one is on?” the Stranger asks on his first fishing trip.

“Will you ever,” the Fisherman replies. “Blues strike like blacksmiths’ hammers.”

So, too, does John Hersey.