IT IS a "law of life," Norman Mailer wrote in The Deer Park , that "one must grow or else pay more for remaining the same."

Our most predictably unpredictable writer does both in his 21st book and fifth collection of short works. It is a chimera of a volume, combining 12 "pieces" from the past decade -- magazine articles, fugitive fragments, prefaces to his own and others' books -- with 20 "pontifications," interviews ranging from 1958 to 1981, Paris Review to Saturday Review, Viva to Vogue . It offers the aggravations and advantages of all such mercenary "greatest-hits" albums: a drear sense of deja vu for initiates; a panoptic utility for those wondering which of the many Mailers is currently predominant.

There are always several. In addition to the public buffoon-savant (a reputation he drags around like an organ-grinder's monkey: "Every time I appear in a newspaper," he admits here, "I injure myself professionally"), there are at least two others -- the pugnacious didact of the essays and the more disinterested protean artist of the books. For the latter, the '70s were rich years, ending in the triumph of The Executioner's Song . For the polemical pug, however, it was a decade of creeping entropy, presaged by Mailer's lackluster introductory admission that he "was much out of step with the Seventies. Still, one does one's best."

It is a game effort. As the topics wander from TV, graffiti and the CIA to Henry Miller, the movies and more, Mailer rummages across the cultural landscape in search of metaphysical meaning, invoking again his trademark theomachy: the neo-Manichean conflict between an embattled god who doubts himself and an ill-defined devil whose handiwork may include cancer, plastic, televised "antimatter," bad architecture, dishonest sex, and the technolgical state.

Along the way, he proves revealing on Miller: "A narcissist is not self-absorbed so much as one self is immersed in studying the other. The narcissist is the scientist and the experiment in one." Eloquent on the paranoid world of intelligence: "Authoritative disclaimers by CIA officials bear the same relation to fact that the square root of one minus one bears to a real number." Provocative on the future of marriage, which "is soon going to be equal in difficulty to pitching a no-hitter . . . . The virtuosity of the demand is finally going to keep marriage alive." Candid on his own sexuality: "male artists have more of a female component to their nature than the average male. I think that's why I've always stayed away from homosexuality."

And Mailer's rococo prose -- frequently mannered, always impelling in its muscular elegance -- has developed an even finer rhythm, whether describing the "limbo" of a deep funk ("all those faceless fornications that rang in the ears, those stupors that drifted like bad weather, apathies piling on apathies like old newspapers") or the psychic vectors converging on a ghetto graffiti artist "chilled on one side by the bleakness of modern design, and braincooked on the other by comic strips and TV ads with zooming letters . . . gut-picked by the sound of rock and roll screaming up into the voodoo of the firmament with the shriek of the performer's insides coiling like neon letters in the blue satanic light, yes, all the excrescence of the highways and the fluorescent wonderland of every Las Vegas sign frying through the Iowa and New Jersey night, all the stomach-tightening nitty gritty of learning to spell was in the writing, every assault on the psyche as the trains came slamming in."

But often the results seen strained -- partly from the effort of stretching his cosmological fabric to cover a new decade, partly because he seems less assured of his own method. At the core of Mailer's genius has been the belief that the nature of being, once dimly intuited, can be investigated through language itself -- that a powerfully apt metaphor is a trustworthy form of inquiry, even augury. "Science, for most of its history, was essentially a poetic endeavor," he explains in the interviews, because "the equation sign is nothing but a statement of metaphor."

But whereas the epiphanies of Cannibals and Christians (1966) arrived in a blast of certitude, the equations here are lodged in an increasingly desperate subjunctive. His Esquire essay on TV promises much: "brooding over the nature of television. As soon brood over the nature of cancer gulch! Might they not be the same? A piece of plastic in the tissues of communing, a pollution in the avatars, good old-anti-matter living next to matter." But beyond a few tepid insights ("you did not make love to your wife after watching TV for an evening. Something had entered the blood") and a grand analogy (television's "message was equal to Nixon's: I am here to deaden you -- you need it") the leaden subject refuses to transmute, and 50 pages later "He knew only that Limbo was looser now . . . . " Nothing is revealed. (Except a rediscovery of Mailer's masterful narrative powers. Among the sardonic video vignettes is a hilarious snipe-by-snipe account of the fabled Mailer-Vidal spat on the Dick Cavett show.) A similar enervation saps "The Faith of Graffiti," where the Aesthetic Investigator can only conclude that "As we lose our senses in the static of the oncoming universal machine, so does our need to exercise the ego take on elephantiastical proportions." And a long mediation on the CIA and Watergate finally urges only "a vision of reality which would recognize that Franz Kafka is the true if abstract historian of the modern age, and the Moebius strip is the nearest surface we can find to a plane."

Finally, Mailer proves most confident here as a storyteller (in the descriptive sections of the essays, in a painterly reminiscence of Harvard, in the chatty circumspection of the recent interviews), most surprising in "Pontifications." Under pressure of questions, Mailer's mind is spectacularly volcanic. Naturally, much sludge comes up with the ore. So for every erupting insight into Ann Beattie or Borges or Garcia Marquez, every brain-rattling metaphysical quake ("sex that makes you more religious is great sex" or "there was always art in the criminal act -- no crime could ever be as automatic as a production process") there is a lumpy moronism like, "I think that the average black knows more about life than the average white in America . . . . I've never met a stupid black man."

But Mailer fascinates even when he falters. Few writers so unfailingly challenge our perceptions and explode our complacencies. And none takes more risks in more ways: "You can never understand a writer," Mailer says here, "until you find his private little vanity and mine has always been that I will frustrate expectations. People think they've found a way of dismissing me, but, like the mad butler -- I'll be back serving the meal.