Call it one of the most remarkable success stories in modern publishing history.

Since late 1985, at least 20 books by Scientology founder L. Ron Hubbard have become bestsellers.

In March of 1988, nearly four decades after its initial publication, Hubbard's "Dianetics: The Modern Science of Mental Health" was No. 1 on virtually every best-seller list in the country--including the New York Times.

Ten hardcover science fiction novels Hubbard completed before his death four years ago also became bestsellers, four of them simultaneously on some lists.

The selling of L. Ron Hubbard was envisioned, planned and executed by members of the Church of Scientology, who say that worldwide sales of Hubbard's books have topped 93 million. The sales have been fueled by a radio and TV advertising blitz virtually unprecedented in book circles, and has put on the map a Los Angeles publishing firm that eight years ago did not even exist.

In some cases, sales of Hubbard's books apparently got an extra boost from Scientology followers and employees of the publishing firm. Showing up at major book outlets like B. Dalton and Waldenbooks, they purchased armloads of Hubbard's works, according to former employees.

As a writer, Hubbard was extremely prolific. He wrote short stories. He wrote books. He wrote screenplays. And, for more than 30 years, he wrote thousands of directives and scores of personal improvement courses that form the doctrine of Scientology.

The promotion of Hubbard's books is part of a costly and calculated campaign by the movement to gain respect, influence and, ultimately, new members. In the process, Hubbard's followers hope to refurbish his controversial image and position him as one of the world's great humanitarians and thinkers.

Hubbard's writings have become a means by which to spread his name in a society that often equates celebrity with credibility. It is not with whimsy that the church often calls its spiritual father "New York Times best-selling author L. Ron Hubbard."

The church once summed up the strategy in a letter recruiting Scientologists for Hubbard's public relations team, an operation that thrives despite his death. Sign up now, the letter urged, and "make Ron the most acclaimed and widely known author of all time."

But apparently Hubbard's followers have not trusted sales of his books entirely to the fickle winds of the marketplace.

Sheldon McArthur, former manager of B. Dalton Booksellers on Hollywood Boulevard in Los Angeles, said, "Whenever the sales seem to slacken and a (Hubbard) book goes off the bestsellers list, give it a week and we'll get these people coming in buying 50 to 100 to 200 copies at a crack--cash only."

After Hubbard's first novel, a Western adventure called "Buckskin Brigades," was re-released in 1987, the book "just sat there," recalled McArthur, whose store was across from a Scientology center.

"Then, in one week, it was gone," he said. "We started getting calls asking, 'You got 'Buckskin Brigades?' " I said, 'Sure, we got them.' 'You got a hundred of them?' 'Sure,' I said, 'here's a case.' "

Gary Hamel, B. Dalton's former manager at Santa Monica Place, had similar experiences. He said that "10 people would come in at a time and buy quantities of them and they would pay cash."

Hamel also speculated that some copies of a Hubbard science fiction novel were sold more than once.

He said that while he was working at the B. Dalton in Hollywood, some books shipped by Hubbard's publishing house arrived with B. Dalton price stickers already on them. He said this indicated to him that the books had been purchased at one of the chain's outlets, then returned to the publishing house and shipped out for resale before anyone thought to remove the stickers.

"We would order more books and . . . they'd come back with our sticker as if they were bought by the publisher," Hamel said.

Hubbard's U.S. publisher is Bridge Publications Inc., founded and controlled by Scientologists--something that Bridge does not publicize. Company officials refused to be interviewed about book sales or any facet of the firm's operations.