“Manson in His Own Words, As Told to Nuel Emmons.” Illustrated. Grove Press, 232 pages, $16.95.

Charles Manson in his own words? Why would anyone want to hear them?

Why would anyone want to do so, even knowing that, according to the book’s introduction, the convicted mass murderer who is its subject is getting “no royalties or any other remuneration from this book”?

We should hear his words to demythologize the monster, argues the author, Nuel Emmons, a reformed auto thief who got Manson to tell his story after reminding him of their early prison days together.

“Most people see Manson and his co-defendants as callous, cold-blooded, dope-crazed killers,” writes Emmons, who is now an auto repair man and free-lance photojournalist. “But others accept Manson as a leader and a guru with mystical powers. They champion Manson, defend him, and try to imitate the life he led before the murders. He has received thousands of letters and numerous visitors during his confinement: letters from teenagers and adults of both sexes; visits from women wanting Manson’s love and attention, from seekers of advice, from would-be followers. They even offer to commit crimes for him — or rather, for the myth that has grown up around him. But the myth is very different from the reality.”

So Emmons, having by slow degrees won Manson’s trust and cooperation, spent seven years interviewing his subject and putting together his story. Manson cooperated because, he says, “the load” of the myth “is too heavy to carry this many years. I want out from under it.” Emmons believes that “the myth of Charles Manson is not likely to survive the impact of his own words.”

Maybe not, at least if the reader accepts the book’s most obvious message. This is the one that portrays its subject as a kid who never had a chance — an illegitimate child rejected by his mother at the age of 12, installed in a reform school where he was beaten and raped by sadists, and ultimately forced into a life of crime because he couldn’t make it any other way.

Not that Manson is excusing himself. It’s just that “it’s obvious there is something lacking in my makeup.”

In any case, at the time of the murders his “family” committed with his admitted encouragement, “I was a half-assed nothing who hardly knew how to read or write, never read a book all the way through in my life, didn’t know anything except jails, couldn’t hold on to my wives, was a lousy pimp, got caught every time I stole, wasn’t a good enough musician to hit the market, didn’t know what to do with money even if I had it and resented every aspect of family life.” But a week after one of his followers, Susan Atkins, sold a copyrighted story, “Two Nights of Murder,” to The Los Angeles Times and several foreign newspapers, “I was a charismatic cult leader with a family, a genius who could program people into doing whatever I asked of them.’

In reality, he concludes, “I’m nothing but the reflection of evil that goes through the minds of all those people who created the monster and keep pushing the myth to kids who don’t know any better.”

The problem is, there are several other Charles Mansons who inadvertently emerge from these pages, among them the strutting show-off, the wheedling whiner, the five-and-dime psychologist and the apostle of univer-sal love. Most disturbingly, there is the Manson who emerged from a federal prison in 1967 and suddenly found himself able to enlist the young women who were to form his murderous “family.”

By CHRISTOPHER LEHMANN-HAUPT