A Writer in Paradise : Fiction: Life in republican Rome is the subject of author Colleen McCullough’s new book, which already is a national best seller.

You have to get the whole picture:

This rather large lady lives on an island in the South Pacific that is said to be more perfect than paradise. The island is three miles long and five miles wide. Her husband, 6-foot-3 and 270 pounds, farms palm trees.

She dresses in billowing cotton pajamas. She eats glorious fresh fruit. She has a swimming pool, a garden and a house with, the last time she counted, 30 rooms. And every day, this lady, Colleen McCullough, surrounds herself with acquaintances who have been dead for 2,000 years.

Cicero: “I was reading the letters of Cicero, those marvelous letters of Cicero to Atticus,” McCullough said. “It is so extraordinary to read them. In one letter, Cicero says: ‘That woman has finally quit Rome.’ ” McCullough looked jubilant. “He was talking about Cleopatra!”

Julius Caesar: “It is rare in history to be lucky enough to read the words of the man who ran the place.” Unfortunately, said McCullough, “Caesar never put a foot wrong.”

Caesar’s apparent faultlessness knocked him out of the running for the role of hero in McCullough’s latest literary endeavor.

“It’s very hard to make a hero who does nothing wrong,” the author of “The Thorn Birds” and four other novels said.

So there on Norfolk Island, not far from where the mutiny on the Bounty took place, McCullough crafted new heroes to fill six volumes of fiction about life in republican Rome. The debut novel in the series, “The First Man in Rome” (William Morrow & Co., $22.95), was published Oct. 1, arrived on the Los Angeles Times best-seller list on Oct. 14, and on Sunday moved on to the New York Times national best-seller list.

Men and women run around in togas in McCullough’s new novel. Their names and the places they live and visit are so complicated that McCullough has included a 15-page glossary. The research took 13 years--”10 years of dabbling and three years of sitting down and doing nothing else.”

It probably would have been easier, and undoubtedly less risky, to write a sequel to “The Thorn Birds,” McCullough’s best-selling contemporary family saga of 1977. But, she said, “I had always wanted to do a really fat historical novel.”

No two of her books are in the same genre, she explained. “I mean, I’m hopeless,” she pronounced, plopping herself down in a chair in her hotel suite here. McCullough has hair that seems to march to its own brush. Her black-patent leather shoes have fake leopard-skin trim. Instead of lunch, McCullough takes a swig of paregoric, because her stomach is bothering her, and lights the first of an endless, unapologetic chain of cigarettes.

“I read anything,” McCullough said. “Everything.”

Thwarted in her search for an ashtray, she commandeers a candy bowl. “I can still tell you what is written on the toilet paper in the public bathrooms in London.” On the top of each sheet, said McCullough, are the words “London County Council.” On the bottom, “Now please wash your hands.”

“I like to read in every genre,” she said--and also, to write in them. “So anyway, a historical novel I knew I couldn’t do until I had enough money not to have to work for a living.” Fortunately, “I have not since ‘Thorn Birds.’ ” To emphasize her point, McCullough threw back her head and laughed. “I ain’t hurting for a quid,” she said.

But to do an historical novel, McCullough knew she needed to find a period that had not been done. “I like to be fresh,” she said. “And I really came across it when I was reading the letters of Cicero and Julius Caesar.”

Now McCullough is just the kind of person who would be reading ancient letters for recreation. A science major at the University of Sydney, McCullough became concerned that she “had never acquired much culture,” and signed up for a classics course. “We read everything,” she said. “It was wonderful.”

Years later, after the publication of “The Thorn Birds,” McCullough decided to reread the classics. “I thought I would love to do it again.” Unmarried well into her 40s, McCullough thought it seemed an appropriate pastime--”life being serious when you are a spinster, and expecting to remain a spinster.”

Early on in the years after “The Thorn Birds,” McCullough began to feel unsafe. She had lived alone since she was 18, but with the fame of “The Thorn Birds,” she said, “there were threats, and all sorts of weirdos popping out.”

A friend suggested Norfolk Island, where the mutineers from the Bounty were resettled in 1856. Residency was by permission only, but McCullough quickly qualified.

“I was at the time in my early 40s, therefore I wasn’t going to be a strain on the local hospital,” she said. “I was wealthy enough that I wasn’t going to be a strain on the economy. No. 3, I had no children, so I wasn’t going to be a strain on the school.”

Soon after she arrived on Norfolk Island, “I was lucky enough to meet, for want of a better word, one of the natives.”

Cedric Newton Ion-Robinson, a.k.a. Ric, “had just sunk all his money into palms.” Since “all those palm trees that you see in hotel foyers all over the world started life as seeds on Norfolk Island,” palm farming can be “very, very, very” lucrative.

Just then, Robinson’s wife “packed up and left him,” McCullough said.

“She let him go.”

“Really,” she added, “that’s the trouble with women. They never know when they’re well off.”

But things worked out well for McCullough and Robinson, a descendant of the Bounty mutineers. “The next thing you knew, we were married.” Another toss of the head, and another big laugh. Since Ric is 13 years her junior, “I am Mrs. Robinson.”

To guarantee the new book’s historical accuracy, McCullough employed a multilingual research assistant. “She traveled around the world, interviewing people on my behalf,” locating, for example, “the world’s expert on the Roman saddle.” McCullough herself drew sketches of all of her characters as she wrote about them.

Historical fiction can be chancy, McCullough conceded. Academics in particular are often quick to attack the credibility of these novels.

But “times are changing,” McCullough said. Money is tight and attendance is down at many universities, and “history departments are one of the first to feel that economic crunch,” McCullough said.

“So anything that popularizes ancient history” is seen as a good thing. She flashed a big smile. “So, I will popularize ancient history.”

Ancient Rome was a jumping place, McCullough said. “It’s so interesting and juicy and meaty that I would love the whole world to know what went on there.”

McCullough’s total-immersion approach to writing this series gave her an edge on some historical novelists, she said. “The thing that I object to in many historical novels is that the characters think in the present.” By contrast, McCullough’s characters “think like Romans.” This is possible, she said, “because when I was writing, I was a Roman.”

Six volumes on ancient Rome seemed no more daunting to McCullough than any other work of fiction.

“I’ve always written novels, always, since I was 5 years old,” she said.

But as a Depression child, “You never announced to anyone that you were going to write novels.” McCullough made science, neurophysiology, her “bread and butter.” It was during her 10 years as a research associate at the Department of Neurology at Yale University that McCullough wrote her first novel, “Tim,” and completed the manuscript for “The Thorn Birds.”

The success of “The Thorn Birds” made science “impossible,” McCullough said. “To do useful work, I needed to be faceless, anonymous.” Suddenly, at dinner parties, “I was being introduced as ‘our novelist.’ ”

So McCullough fled to the sanctity of Norfolk Island, where, she said, “This is what I do. I just sit down and write books.”

There in her tropical Eden, hard-core workaholic McCullough writes at least eight to 10 hours each day.

Having written her love story (“Tim,” 1974); her family saga (“The Thorn Birds,” 1977); her whodunit (“An Indecent Obsession,” 1981); her novella (“The Ladies of Missalonghi,” 1987), and her future tale (“A Creed for the Third Millennium,” 1985). McCullough can now add history to her dance of the genres. She is two-thirds finished with the second in the Roman series, and promises that “it’s even better than the first.”

And so, next?

“Next I think I will do something contemporary, nasty, bitter and steamy,” McCullough said. She thought for a moment and decided she liked that idea. “Yes, something steamy, after the Romans.”