BUNNY; The Real Story of Playboy. By Russell Miller. Holt, Rinehart and Winston 371 pp. $16.95.

THE DEBTS our culture owes to Hugh Marston Hefner are almost too numerous and great to fathom, though a family newspaper is not necessarily the place to discuss them in the detail they so richly deserve. We have Hugh Hefner to thank for the exhaustive considerations of matters sexual and gynecological in public forums so diverse, if uniformly enlightening, as "The Playboy Advisor" and The Phil Donahue Show. We have Hugh Hefner to thank for the spectacle of two national magazines competing to be first on the newsstands with their explicit nude photographs of a rock-'n'-roll singer bearing the unfortunate name of Madonna. We have Hugh Hefner to thank for the pervasive presence of sex, whether overtly or by innuendo, in virtually every corner of our public life from sitcoms to soap operas to advertising.

It is a statement to be made without an ounce of pleasure, but it is an inescapable fact: Hugh Marston Hefner is one of the most influential Americans of the postwar era. He is the high priest of "sexual liberation," and his presence in our lives, however odious it may often seem, is appallingly large. If public sex is now an everyday fact -- relentless, humorless, leering, exploitative sex -- it can all be traced back to the fall of 1953, when Hefner produced the first issue of his new magazine. Originally it was to have been called Stag Party, and if it had been perhaps we'd have been spared much if not all that followed. But it was called Playboy and the rest, alas, is history.

As told by Russell Miller in Bunny it is marvellously entertaining history. This is no peep-and-wink production, but a solidly reported piece of cultural journalism that skewers Hefner not by diatribe or homily but by the sheer accumulation of damning evidence. The portrait Miller paints of Hefner is all the more devastating precisely because it is far from unsympathetic; he gives the devil his full due, crediting him with an impressive record of personal and professional loyalty, a discerning editorial eye, and the "important contribution" to American journalism of the in-depth Playboy Interview. He gives him all that and more, but in the end the portrait is of "a man in late middle age who refuses to grow up, who lives in a house full of toys, who devotes much of his energy to playing kids' games, who falls in and out of love like a teen-ager, who enjoys pajama parties and is cross when his gravy is lumpy."

There can be no doubt, either from Miller's account or from the evidence presented by Hefner himself in Playboy and his other works, that it all boils down to perpetual adolescence. Throw away the window dressing -- the pretentious interviews, the second- rate short stories and articles by famous writers, the self-righteous defenses of free speech -- and Playboy is nothing except a teen-aged boy's fantasy magazine, its pages filled with titillating pictures of impossibly busty girls, their skin creamier than anything Elsie the Cow ever manufactured, their promise of eager submission positively leaping off the page. Alone in his room with a magazine like that, a boy can be just about anyone he wants to be: Casanova, Lothario, Don Juan, even Hugh Marston Hefner. It just about takes a boy's breath away:

"The Playboy Mansion was the house of Hefner's dreams, yet there were times when he could hardly believe his dreams were coming true. Shortly after taking up residence at 1340 North State Street Parkway, he made notes in his scrapbook in the breathless, gee-whiz, student idiom that he still employed, even though he was by then in his mid-thirties. 'It's difficult to bring into perspective and fully appreciate, but we are truly becoming, in our own time, a legend. And what does it feel like, being a living legend? Well, it feels just great!" Y

OU BET your booties it does, especially when you're swinging in your Mansion -- either one will do, Chicago or Los Angeles -- with all your pals and your Bunnies and your Playmates. First you have a private screening of a movie (you and your current lady get to occupy the sofa in front-row center), then you all troop over to the Games House for some serious Space Invaders and Pacman ("A special kid glove is kept on the Pacman machine, his favorite, so that he does not get calluses on his hand from wrestling with its single joystick control"), then it's off to the Woo Grotto: "The warm, scented waters, the changing colors of the underwater lights, the soft piped music, the caress of the jacuzzi, what more could lovers want except, perhaps, a little privacy?"

It's a boy's dream come true, and it's the key to Hefner's uncanny success. "He made no secret of the fact that he produced the magazine for himself," Miller writes: "it unashamedly pandered to his fantasies. He wanted to be a suave, sophisticated man- about-town, sexually liberated, irresistible to women, and a masterful lover. Thus it was to this fantasy figure that Playboy magazine made its pitch. It was an unbeatable formula." If anything, "formula" may be too charitable a word for it. Like Topsy, Hefner's empire just growed, each new addition to it merely another accomodation to the surges of its master's libido. First the magazine, then the Playmates ("white, young, blonde, wholesome, American, and always available"), then the Playboy Clubs and their Bunnies, who "offered the thrill of sex without the threat of having to do anything about it."

There wasn't any master plan behind the shaping of this colossus of sex, and in fact it was when executives started trying to draw one up -- when they stopped listening to Hef's fantasies and started watching the bottom line -- that there began to be trouble in paradise; undertakings that had less to do with sex than with money, such as casinos and resorts, were little but trouble from day one. Beyond that, Hef suddenly found himself outflanked on the sex front. In 1969 along came Bob Guccione and a magazine called Penthouse, in which within almost no time he had crossed the great divide and published photographs to which no airbrush had been addressed. Caught off guard, Hef had to respond quickly; the result was what the industry called the Pubic Wars, in which each magazine sought to be more explicit than the other -- and which other combatants soon entered, most eminent among them Hustler and its singular publisher, Larry Flynt.

It was a pretty nasty business, and it did little to discourage Hefner in his retreat from the real world into the seductive comforts of the Mansions. While tumult raged outside -- the heavy investment in Roman Polanski's disastrous Macbeth; the alarming sag in Playboy circulation and ad revenues; the extreme difficulties with the Playboy Club casino in London; the shaky, rivalrous condition of the company's upper management -- the Howard Hughes of sex disappeared into Playboy Mansion West, where by 1983 it was costing the company more than $3.5 million a year to accommodate the needs of Hef, his pals and their gals. This expense is countenanced by the company's new president, Hefner's daughter Christie, a tough and resourceful manager who somehow does not seem to have it in her to take Daddy's toys away from him.

So Hef plays on, "a recluse in silk pajamas who believes he can stay in touch with the real world without emerging from the pampered womb of the Playboy Mansion in Los Angeles," an aging rou,e who fancies himself Romeo but is closer to Alexander Portnoy. As Russell Miller well knows, Hef will not like this book. Bunny is thorough, incisive, unsparing and deliciously funny, all of it at the expense of Hugh Marston Hefner. It's almost been worth everything Hefner has put us through, just to watch him get so thorough a comeuppance in this thumpingly good book.