Jeff Koons is in but not of that little club. He’s as famous as any of its members, though loved and hated in equal measure. (Sometimes all at once, by the same people.) Yet despite his self-created and enigmatic otherness, he is also the emblematic artist of the decade -- its thumping, thumping heart.

Koons’ work has always stood apart for its one-at-a-time perfection, epic theatricality, a corrupted, almost sick drive for purification, and an obsession with traditional artistic values. His work embodies our time and our America: It’s big, bright, shiny, colorful, crowd-pleasing, heat-seeking, impeccably produced, polished, popular, expensive and extroverted -- while also being abrasive, creepily sexualized, fussy, twisted, and, let’s face it, ditzy. He doesn’t go in for the savvy art-about-art gestures that occupy so many current artists. And his work retains the essential ingredient that, to my mind, is necessary to all great art: strangeness.

You can see this in his glorious phantasmagorical masterpiece, the large-scale topiary sculpture Puppy. This 40-foot visitor from another esthetic dimension appeared in New York in the first year of the new millennium. It assumed the form of a West Highland white terrier constructed of stainless steel and 23 tons of soil, swathed in more than 70,000 flowers that were kept alive by an internal irrigation system. The sculpture was fabricated in Germany in the early ‘90s, and it took eight years for Koons to bring Puppy to New York, where he plopped it down in front of the G.E. Building in Rockefeller Center, where the Christmas tree now stands. All through that blithe summer of 2000, amid a happy haze of peace and prosperity, crowds came to gawk at this bountiful botanical Buddha -- an indolent idol from the artistic id. Like an early Beatles song, Puppy just made people happy. Even contemporary-art haters responded to it with grudging warmth. Unlike most public art, it reached out to viewers, and they responded. It was the antithesis of Richard Serra’s Tilted Arc tonnage, which haughtily, icily demanded your respect. This was, after all, a puppy. It might lick your hand.

All of Koons’ best art -- the encased vacuum cleaners, the stainless-steel Rabbit (the late-20th century’s signature work of Simulationist sculpture), the amazing gleaming Balloon Dog, and the cast-iron re-creation of a Civil War mortar exhibited last month at the Armory -- has simultaneously flaunted extreme realism, idealism and fantasy. Puppy adds to that: It is a virtual history of art, recalling the mottled surfaces of Delacroix (albeit on ’shrooms), the fantastical fairy-tale beings of Redon, a mutant Frankenstein canine from Seurat’s La Grande Jatte, and the eye-buzzing Ben-Day dots of Roy Lichtenstein. As it emits the swirling amorphousness of Tiepolo and the pathos of Watteau, it is also a magnified, misshapen abstraction of Duchamp’s urinal -- a similarly deliberate gesture of antic outlandishness, and one that, of course, was signed "R. Mutt."

But most of all, Puppy is a telling self-portrait of an adamant, anxious, infatuated and troubled soul. Despite Koons’ cheerful Ronald Reagan optimism and daffy pronouncements (he called Puppy "a contemporary Sacred Heart of Jesus"), just beneath the surface of the sculpture and its maker is an obsessive rage. Koons is a driven perfectionist in pursuit of unconditional love, and his Puppy is at once an overeager peace offering and a Trojan Horse declaration of war.

Koons, after all, has risen from the ashes. After his 1991 "Made in Heaven" exhibition, in which we saw graphic depictions of Koons and his ex-wife, the porn star La Cicciolina, having sex, Koons was shunned within the art world. He wasn’t invited to biennials; he had only one more New York solo gallery show in the ‘90s. To get a sense of how that felt to Koons, consider that he once mused about being "burned at the stake."

So he spent most of the ‘90s working to return to New York with something utterly perfect, powerful and beyond criticism. Puppy accomplished that. Not only was it an instant icon; it is the first piece of art exhibited in the 21st century that was clearly jockeying for pop-culture supremacy. Christo and Jeanne-Claude’s ho-hum Gates or Olafur Eliasson’s East River waterfalls would follow, without generating Puppy’s sparks of weird delight.

Koons’ fearsome urge toward order was demonstrated to me a few days before the sculpture’s June 6, 2000, unveiling. One warm evening I stopped by the GE Building to see Puppy’s progress. No one was around except Koons, wearing a green plastic hard hat. He amiably greeted me, and, after a bit, asked whether I’d like to set a flower in place. "Would I ever!" I replied. He told me to pick a flower from a nearby tray and place it "anywhere you want." I picked up a petunia, eyed Puppy, and set it in a front paw. I was thrilled. "That’s great, Jerry," Koons said, before pausing, pulling my petunia out, and moving it a centimeter to the left. Now I was flabbergasted.

But that moment crystallized what Puppy and its artist were about. There were 70,000 separate decisions involved in Puppy. Every flower had to be placed exactly right. It was mad! (Puppy remains a demanding pet: Its owner, the megacollector Peter Brant, spends upwards of $75,000 per year maintaining it.) Koons was attempting to control chaos at the very moment when chaos was beginning its reign.

Puppy was the first of this decade’s public-spectacle art extravaganzas, but it also marked the end of something, and the deepening chasm between sincerity and irony, joy and menace, life and decay. It is the last of a kind, a prelapsarian still point of perfection and innocence in a dissolving landscape of obliviousness. Puppy appeared at the end of a happy interregnum, after the Berlin Wall came down, before the economy disintegrated and the towers fell. It is an artifact from the last days of "the end of history." We didn’t know it at the time, but what Victor Hugo called "the deepening of shadow" was happening around us that summer. With Puppy, Koons laid a beautiful, ghastly laurel wreath at our doorstep. If it could speak, it would say, "After me, the deluge."

JERRY SALTZ is art critic for New York magazine, where this essay first appeared. He can be reached at jerry_saltz@nymag.com.