In a decade as Random House's editorial consigliere to Mario Puzo, I never once saw him lose his temper or express any form of anger. He was an unusually serene and gentle man, characteristics that made the ruthlessness of his fictional characters all the more surprising.

I do, however, recall a rare moment of exasperation, one that strikes me as being the truest expression of who Mario Puzo, who died Friday, really was. It was the summer of 1996 and Mario, after years of public silence, had agreed to talk to journalists about his life and the writing of "The Last Don," his first Mafia novel since "The Godfather." Despite having created a cultural landmark, Mario was nervous about the interviews and asked me to be present for them.

The conditions for all of the interviews would be the same. They would be held in Mario's spacious Bay Shore home on Long Island, decorated simply with thick carpeting and framed posters of his books and movies. We would ascend to the second floor and sit on the couch where Mario dreamed up his tales of treachery and vengeance. After the conversation, we would descend to the dining room, where a generous assortment of cold cuts and fresh mozzarella would be served. In the adjacent living room, on opposite ends of the mantel, the reporter could see Mario's two Academy Awards for co-writing the screenplays for "The Godfather" and "The Godfather, Part II."

The moment of exasperation came when a journalist raised the inevitable question about the Mafia and Mario's personal connections. He was used to this line of inquiry and always had a disarming way of swatting down the question. (My favorite was his assertion that if he really did have connections, the film adaptation of his novel "The Sicilian" never would have been released.)

In this instance, though, Mario expressed utter bafflement with the persistence of the rumors. "I don't understand it," he said. "I'm a literary man." He said it firmly, with emphasis: "I'm a literary man."

Reading, he once told me, was the one pleasure that had not diminished with the passing years. Diabetes and heart disease had limited his mobility and curtailed his diet, but his appetite for books was inexhaustible. He spent thousands of dollars every year at the local bookstore, and his den was littered with everything from the writings of Dennis Rodman to a worn paperback copy of Larry McMurtry's "Lonesome Dove," a book for which he expressed reverence on numerous occasions.

He read everything, from Anita Brookner to John Grisham, from Oscar Wilde to his personal favorite, Feodor Dostoevski, who shared his fascination with the hearts of villains and the villainy in all our hearts.

Mario was sometimes disappointed by current bestsellers, especially the ones with shallow characterizations and weak endings. When he was a struggling writer, he did book reviews for $50 apiece, but after his success with "The Godfather," he refused all assignments. He told me that he knew how hard novelists worked on their books and he couldn't bear to break their hearts, so he chose to say nothing at all. Once, after a phone conversation in which he criticized a current book, Mario called me back to apologize for speaking ill of a fellow author.

He was acutely aware of his own strengths and weaknesses as a writer. In his first two novels, "The Dark Arena" (1955) and "The Fortunate Pilgrim" (1964), Mario had labored over the lilt of his sentences and aspired to artistry, to the extent that he once refused a publishing house's offer because the publisher wanted a different ending. When those books failed to attract readers, he changed his approach and focused more on his skills as a storyteller. He was self-deprecating in describing this transition, and he often said he wrote "The Godfather" for the money. That was true, but it is equally true that Mario came to realize that his true gift was for creating mythic morality plays in which only the most ferocious and cunning would survive.

That was his view of life. He was fascinated by power and its use, and suspicious of all public displays of piety. During the Monica Lewinsky episode, he expressed sympathy for President Clinton, who, in Mario's estimation of human frailty, couldn't help using the power he had worked so fervently to attain. "The guy doesn't gamble. He doesn't drink. What else is he going to do?"

Mario spent the last three years of his life writing "Omerta" (Sicilian for "code of silence"), which he considered the final installment in his Mafia trilogy about power and morality in America. I would visit his home on Long Island to read the pages, and he would greet me, barefoot and in sweat pants. As he aged, his round face had begun to resemble that of Vito Corleone at the end of "The Godfather," and Mario himself observed that in his hand gestures and facial expressions, he was behaving more and more like a don. When it became too difficult for Mario to use the stairs, he installed an elevator to take him from his bedroom to the kitchen. He would wave to me grandly from the elevator as he made his descent.

Mario, who was 78 years old, probably knew he wouldn't live to see the publication of "Omerta," but he was determined to finish the book. He wrote it as a gift to his longtime companion, Carol Gino, his five children and his nine grandchildren--a large brood that was intimately involved in his life and gathered frequently at his home. Mario said on several occasions that once he was done writing, "Then I can die." He thought a lot about mortality, and his later books are filled with wonderful scenes of old men confronting death. This is one of my favorites, from "The Last Don":

The world was turning crimson with light, and Gronevelt squeezed his nurse's hand to keep his balance. He could look directly into the sun, his cataracts a shield. He drowsily thought of certain women he had known and loved and certain actions he had taken. And of men he had to defeat pitilessly, and the mercies he had shown. . . . And he was happy he was leaving it all behind.

What Mario Puzo will leave behind are his stories--glorious, romantic myths of thieves and heroes, and the perplexing ambiguities that exist between them.

Jonathan Karp is a senior editor at Random House, which will be publishing "Omerta" in July 2000.

CAPTION: Frank Puglia, left, and Marlon Brando in "The Godfather," which Puzo adapted from his novel; below, Puzo wins an Oscar in 1975 for "Godfather II."

CAPTION: "Godfather" author Mario Puzo, who died Friday at 78. In his mythic morality plays, only the most cunning managed to survive.