Richard Adams was an Oxford-educated public servant when “Watership Down,” his first novel, was published in 1972. (PA Wire)

Richard Adams, a British writer whose novel about rabbits, “Watership Down,” sold 50 million copies and mesmerized generations of readers by creating an ornately detailed fantasy world and subverting the Flopsy-Mopsy stereotype of warm and cuddly bunnies, died Dec. 24 at a nursing home in Oxford, England. He was 96.

He had a blood disorder, said a daughter, Juliet Johnson.

Mr. Adams was an ­Oxford-educated public servant when “Watership Down,” his first novel, was published in 1972. The book follows a band of rabbits who search for a new home after Fiver, the runt of his litter, has a vision of their grassy home ­covered with blood — a result of the land’s being developed by ­people for “high class modern ­residences.”

Led by Fiver’s older brother Hazel, the rabbits journey across woods and stream to arrive at Watership Down, where they battle a totalitarian bunny named General Woundwort before establishing a new, utopian warren.

Expecting a tale of friendly anthropomorphic animals in the spirit of Kenneth Grahame’s “The Wind in the Willows” or Beatrix Potter’s “Peter Rabbit” series, publishers and literary agents rejected “Watership Down” seven times, telling Mr. Adams that it was too childish for adults and too adult for children.

Mr. Adams, holding a pet mouse, in 1974. (Tom Smith/Daily Express/Hulton Archive via Getty Images)

Chapters begin with epigraphs drawn from the Greek tragic playwright Aeschylus and the military theorist Carl von Clausewitz; and Mr. Adams’s leporine world is so detailed as to include rabbit mythology and an onomatopoeic rabbit language.

But discovering that the rabbit word for car is “hrududu” was apparently part of the book’s magic. It won prestigious prizes for children’s literature in England and earned the previously unknown Mr. Adams comparisons to Grahame and J.R.R. Tolkien.

“If there is no place for ‘Watership Down’ in children’s bookshops,” the Economist magazine wrote, “then children’s literature is dead.”

The novel’s appeal, according to Cathryn M. Mercier, director of the Center for the Study of Children’s Literature at Simmons College in Boston, rested as much on its richly textured fantasy world as its apparent parallels to the human world.

“We see qualities of ourselves in those feisty little rabbits,” she said.

In one section, a rabbit named Strawberry offers a rebuke to human ways in an explanation of how animals are different from people: “If they have to fight, they fight; and if they have to kill, they kill. But they don’t sit down and set their wits to work to devise ways of spoiling other creatures’ lives and hurting them. They have dignity and animality.”

Mr. Adams later revealed that the book’s rabbit heroes were based on his commanding officers in the British military during World War II, but he decried attempts to find larger meanings in the novel.

“I promise you it is not a fable or an allegory or a parable of any kind,” he told the Pittsburgh Press upon its release. “It is a story about rabbits, that is all.”

An animated movie was made in 1978, with voices provided by actors such as John Hurt, Ralph Richardson and Zero Mostel. A musical and an animated television series followed.

In a sign of the book’s reach, it even introduced the idea of a rabbit to readers who had never seen one: The covers of some worldwide editions featured gerbils scampering over sand dunes.

Richard George Adams was born in Newbury, England, on May 9, 1920. He was the youngest of three children, the son of a nurse and a father who, when he wasn’t working as the local doctor, tested Mr. Adams on the names of the birds and other wildlife that ­surrounded their home, urging him to learn, as well, his knotgrass and pimpernel, heartsease and speedwell.

As a “kind of joke” and nod to his status-conscious father, Mr. Adams used early royalties from “Watership Down” to buy a genuine coat of arms for himself, appropriately featuring three rabbits on a green ground.

With the outbreak of World War II, he left the University of Oxford to enlist in the Royal Army Service Corps. He later joined a British army airborne division but never saw combat.

He completed his degree after the war. He received an honors degree in modern history in the late 1940s, also from Oxford, and moved ­directly into the British civil ­service, where he spent the next two decades.

Working on issues as varied as slum clearance, outdoor advertising regulations and the Thames Flood Barrier, a London landmark, he rose to the position of assistant secretary in what would later become the Department of the Environment. Because of the amount of information Mr. Adams was required to gorge and synthesize, the job was “good training for a novelist,” he later told People magazine.

His writing career happened almost by chance. Mr. Adams had children late in life and liked to entertain them with stories. In 1966, driving from London to Stratford-upon-Avon, Shakespeare’s birthplace, he began ­telling them about two rabbits named Fiver and Hazel who ­traveled to the real-life Watership Down, five miles from his ­childhood home.

Two weeks later, when he had finished his improvised tale, his daughters urged him to write it down. He completed the book over the next two years.

His next novel, “Shardik” (1974), a religious epic about a bear worshiped as a god, met with mixed reviews and some ­befuddlement for going so far afield from the green grass and warrens where Mr. Adams had made his name.

Critics panned its characters as stilted and one-dimensional, but Mr. Adams considered it his finest work and quit the civil service to write full time after its release. He took his library, family and money to the Isle of Man, a British Crown dependency, to escape higher English taxes.

His apparent disdain for ­negative reviews was tested by his later novels.

The Plague Dogs” (1977) chronicled the escape of two dogs from an experimental laboratory in England’s Lake District. The book presaged his turbulent two-year term as president of the Royal Society for the Prevention of Cruelty to Animals, from which he resigned in 1982 because, he told the London Independent, the leaders “seemed to be more concerned with each other than with the animals.”

The Girl in a Swing” (1980) and “Maia” (1985) were erotic love stories concerned with female sexuality. The books ­coincided with the transition of Mr. Adams’s public image from children’s writer and animal ­advocate to an elderly man with, in his words, “a pretty erotic ­disposition.”

Survivors include his wife, ­Barbara Acland, whom he married in 1949, and two daughters, Juliet Johnson and Rosamond Mahony; six grandchildren; and one great-granddaughter.

For the past three decades of his life, Mr. Adams lived in the small town of Whitchurch, in southern Hampshire. His private library was considered one of England’s finest, with works that included a second folio of ­Shakespeare and a Bible that had belonged to King Charles II.

Mr. Adams wrote a memoir of his early years, “The Day Gone By” (1990), and returned to the rabbits that made him famous just once, publishing “Tales From ­Watership Down” in 1996. The book, a collection of intertwined stories, served as prequel and ­sequel to the original novel.

He seemed at peace with the fact that nothing matched the success of his literary debut.

“I try to look at it in a positive way,” he told the London ­Guardian in 2015, “to say to ­myself, ‘Look at “Watership Down” — if you can do that, you can do any ruddy thing.’

“Of course you can’t expect to have another success like that, but it does give you the confidence and the enjoyment to go on ­writing.”