SAN FRANCISCO, Dec. 15 – He’s not particularly impressive to look at: medium height, modest beard and hush jacket. And he’s quiet, soft-spoken so that you have to listen hard to hear him relate, with some astonishment, how he has suddenly become rich.

Curt Gentry, a young-looking forty-three, who has taken to drinking brandy on the rocks lately, is the co-author, with attorney Vincent Bugliosi, of Helter Skelter (The True Story of the Manson Murders).

Released in November, it is the Book of the Month Club selection for December; which is to say, it’s going to make money. Gentry says a television production company has already purchased an option on it for three ninety-minute specials; the British rights have been sold and W. W. Norton & Company, the publisher, is negotiating for the German rights and paperback rights.

What all of this means is that Gentry and Bugliosi have a winner. Translate that as $150,000 with probably another $150,000 to come if the television shows are finally produced.

Commercial success is a novelty to Gentry, who has co-authored half a dozen books and a travel guide that did little more than keep him eating. Now, the Lamar, Colorado newspaperman (Lamar Daily News, Denver Post) can ignore the mailman with his royalty checks.

Success didn’t come easy to Gentry, who struggled for nearly ten years completing his education at San Francisco State, managing a book store and writing occasional magazine pieces.

He did some part-time book reviewing for the Chronicle, hung on to the book store job and wrote nights. Finally, after completing The Dolphin Guide to San Francisco and the Bay Area and Jade: Stone of Heaven, co-authored with Richard Gump, Gentry was able to go it alone. He began writing full time.

What followed was a succession of books on the West, including Madams of San Francisco and John M. Browning, American Gumnaker. He got into the crime field with Frame-Up, a recreation of the Mooney-Billings murder case. The techniques he polished in Frame-Up appear with brilliance in Helter Skelter. The lean years are now over for Gentry.

“I’ve never had anything like this happen to me before publication,” he said the other day, digging into a rare prime rib.

“What it means is that I can spend two or three years on something I want to do, something that doesn’t have a big commercial potential.” He says he’s thinking of a full length biography on a well-known writer who had once offered him encouragement.

“But I don’t want to say who it is — yet.”

Gentry, the seasoned professional, immediately recognized the commercial potential of the story of the Tate-LaBianca murders and the deranged Manson Family members who killed without motive.

“I had worked before with defense attorneys,” he said, “but this is the first time I went to a prosecution attorney.” Gentry was referring to Bugliosi, who was deputy district attorney for Los Angeles and chief prosecutor of Charles Manson and his Family.

The two became collaborators Bugliosi supplying voluminous trial transcripts, investigation records and legal expertise, and Gentry sorting out the material and putting it in cohesive form, a monumental task.

“The stuff he (Bugliosi) turned over to me …I’ve never seen anything like it. There was enough for three or four books,” Gentry said.

Organizing and writing took him four years. It was a change of pace for a writer who normally allows nine months for a book.

He says he worked about nine hours a day, seven days a week during the four years, “and the worst part of it was that I couldn’t talk about the work.”

Bugliosi had had his life threatened by members of the Family still at large, and the collaborators met secretly in Los Angeles and San Francisco to keep the project under wraps. Bugliosi, at one stage, even had a bodyguard, and Gentry was perfectly aware of the cold-bloodedness of the Manson Family, convicted of seven senseless murders and probably responsible for at least thirty more.

After two years of research, which included wading through the mountains of material and newspaper files on the year-long trial and tracking down fringe members of the family for interviews, the original publisher, Putnam, got impatient.

“They wanted something fast, and there was no way I was going to do it,” Gentry says. “There were too many questions unanswered. I wanted to be able to understand Charlie and the girls.”

As it turned out, W. W. Norton bought up the Putnam contract and gave Gentry the time he needed to do the book his own way. Norton subsequently launched a promotional campaign for the book that took Bugliosi and Gentry on a six-week tour of the country for book store and television appearances. And advance sales are already pouring in.

Gentry, as the reader no doubt will, found the subject scary.

“It was scary to me to find that the Family was able to pick up new converts even after Charlie was in jail.” He interviewed one convert. Maria Alonzo (also known as Crystal), after a tip he received in the no name bar in Sausalito.

“She sounded just like the rest of the Family girls,” he says. Like Susan Atkins who had stabbed the pregnant Sharon Tate sixteen times in the heart, lungs, liver, breast and back.

The horror of the night of August 9, 1969 and the human slaughterhouse that was the home on Cielo Drive in Benedict Canyon is, of course, the central event of the book.

But Gentry puts something into it that the newspaper accounts lacked. He has masterfully arranged the chronology and the long list of characters; he has pieced together the bits of evidence in such a way that the reader, although he knows what happened, is locked into the narrative.

Suspense is maintained by suggesting to the reader that startling disclosures are about to be made —more gruesome than the last.

The writing style plays a part in this. Gentry is economical with the language. A long sentence is thirty words and most of them run eight to twenty words. There’s very little if anything padded in the entire 502 pages.

The book ends with the trial completed and the sentencing of Charles Manson, but there is an interesting epilogue that attempts to trace the causes of the madness that snuffed out so many lives.

“Charlie,” as Gentry calls him, “was an ex-pimp, a small person five foot two who knew how to manipulate people, get them to kill for him.” He had taken a Dale Carnegie in prison; he was a student of Scientol-ogy; he had been likened to Satan, Christ and Hitler.

Says Gentry: “I don’t know what the solution of this sort of madness is…except to try to understand the Charlie Mansons.”

The book, which takes its title from the words scrawled in blood in the LaBianca home, goes a long way toward that understanding.

By TOM EMCH