LIBERACE A Biography By Bob Thomas St. Martin's. 284 pp. $18.95

Surely it is one of the greatest oddities of the odd age in which we live that the two most widely and passionately adored figures of its popular culture should have been Elvis Presley and Liberace. Could two more unlikely heroes possibly be conjured up by a writer of fiction? As musical performers they were decidedly limited, their styles of dress and public behavior carried vulgarity to extremes previously unimagined, and the sexual vibrations they sent forth were, to say the least, both blatant and ambiguous -- yet they were the recipients of adoration quite unmatched since that bestowed upon Rudolph Valentino.

How are we to explain this? Though both men acquired a certain camp following among the intelligentsia, their real audience was in blue-collar America, which sociologists and other students of group behavior repeatedly characterize as socially and culturally conservative. Yet the wild response with which millions of Americans greeted Presley's throbbing pelvis suggested that a mass libido ached to find thundering expression, and the devotion that innumerable women of middle age and older fastened upon the epicene Liberace suggested ... what?

Who knows? But do not look to Bob Thomas' biography of the late and lamented star for answers. In this, as in his many previous lives of stars and other public nuisances, Thomas competently compiles facts and factoids, sets them down in a pedestrian prose style and steadfastly refuses to engage in speculation as to psychology or motive. His "Liberace" is an entertainment and by no means an unenjoyable one, but it is not an interpretation -- and that, surely, is what the bizarre career of Liberace cries for.

He was born in 1919 in Milwaukee, christened Wladziu Liberace, but called Walter in order to accommodate American pronunciation. His father was a grocer and, when work was available, professional musician; the son demonstrated musical gifts at an early age and was encouraged in them by a teacher, Mrs. Kelly, who was "the most important musical influence of Liberace's professional life." But the most important person in his life was his mother -- "Mom" -- a smothering creature who was the embodiment of Philip Wylie's caricature of Momism but who was adored without reservation by her second son.

He struck out early on his own, to Mom's dismay. For a while the going was difficult as he played the piano in clubs and theaters, but as he did so, he gradually evolved a style that expertly blended classical and popular music in a lowest-common-denominator mix. He "required three minutes to deliver a movement of Beethoven's Moonlight Sonata that took Horowitz eight minutes." He did this utterly without duplicity or embarrassment:

"My whole trick is to keep the tune well out in front. If I play Tchaikovsky, I play his melodies and skip his spiritual struggles. Naturally I condense. I have to know just how many notes my audience will stand for. If there's any time left over, I fill in a lot of runs up and down the scale."

He also developed an expert knowledge of how to play to the television camera. His first show was in Los Angeles in the early 1950s, and it quickly became a startling success. A station manager told him: "The thing you do best is communicate with your audience. You make them feel you're playing just for them. That's what television is all about." By the mid-'50s he was a national institution, mincing onto the stage in his garish white silk lame' tuxedo or the black one with 1,328,000 sequins, plumping himself down before a piano festooned with candelabrum, merrily ripping his way through the bastardized classics.

Then rock came along, in the equally garish form of Elvis Presley, and for a time Liberace's career was in danger. He rescued it, though, by finding a niche for himself in Las Vegas and by indulging in deliberate, high-spirited self parody. Though he kept his homosexuality pretty much between himself and his ample supply of pretty young men, he let his act become so gaudy a mockery of gay stereotypes that it was quite impossible not to laugh with, rather than at, him. Everything about him was outrageous and outlandish and wonderful. "I love the fake," he said once. "As long as it looks real, I'll go for it."

The trouble with being fake, though, is that sooner or later reality catches up. By the 1980s Liberace was a hideous wreck: "In his desperate fight against age, his face sometimes resembled a grotesque mask of Liberace of the 1950s. Plastic surgery had eliminated character along with the wrinkles, and makeup contributed to the air of unreality. The pompadoured toupees added to the theatricality." His health, too, began a rapid decline; he died a year ago, of AIDS.

He was mourned ardently, though not with the extreme emotion that had accompanied Presley's obsequies a decade earlier; Liberace, unlike Elvis, at least had come close to living his appointed three score years and 10, and rumors of his terminal condition had been sufficiently widespread to prepare his legions for the inevitable. At his funeral the mood was sad but affectionate; people liked Liberace, and remembered him fondly.

This no doubt is an important part of the Liberace mystique; he was a genuinely nice man, who really meant it when he called himself "a person who was put on earth simply to bring happiness and love to people," and his followers were willing to overlook his more egregious behavior because they cared for the innocent, childlike man within. But they also liked his behavior, even if in their own lives they may have had no tolerance for homosexuality. Liberace's flamboyance was a wicked sendup of high culture and a mockery of middle-class convention. Somewhere inside all of us, there is a rebel and nonconformist; no doubt it was this, as much as anything else, that responded so enthusiastically to Liberace and his gay buffoonery.