Why do we stare at the David? What is it about that seventeen-foot-tall Michelangelo that so transfixes, spellbinds the human eye and stops it, frozen by some Olympian opiate, before that dwarfing marble nude? Do we dare to marvel at human ideality in an exercise of our own vanity? Do we search for ourselves in the lifeless stone or do we stand in awe at what we could never be, glued to David’s marble skin by the sheer horror of perfect beauty, of eternal perfection?

“It’s like a magnet,” writes Joshua Harmon in his new play, “Skintight.” “It pulls you in, physically,” says one of his characters, sitting in a jock-strap on a couch in a multi-million-dollar West Village brownstone, chiseled into his own flawless image of male form. “You can see a tourist’s face change as they get closer, like there’s something in their bones…they can’t walk away cause they can’t deny the power of—,” he pauses.

“Beauty,” someone answers.

So lies the heart of Joshua Harmon’s new play, produced by Roundabout Theatre Company at the Laura Pels Theatre. Beauty — not beauty for nature’s sake, not beauty as it exists in harmony with creation, but beauty for vanity’s sake. Self-creation and perfection, narcissism and youth, lust and eroticism, perversion and voyeurism. From a playwright (“Significant Other”) who has chosen the eccentric, sociological boundaries of life in millennial America as his muse, comes a play solely about the service of beauty, the utility and centrality of vanity in modern life, its sanctity in the self-centered, contemporary American way.

And while a project about the deification of self-creation may seem like an aged zeitgeist, a conversation that feels more or less at home in the mid-2000s, Harmon sets his play in a present-day, West Village brownstone whose interior feels like a Los Angeles health spa rather than a human dwelling, more like a plastic surgeon’s waiting room than any living space.

It’s the mansion (and a brilliant, well-thought-out set by Lauren Helpern) of Elliot Isaac (Jack Wetherall), an internationally known fashion designer the likes of some real life, rags-to-riches fashion mega-brands like Tommy Hilfiger. It’s a home that the fictional designer has created to sanctify, to cryogenically freeze the youthfulness that escapes him. It’s a chic, nearly dystopic urban home whose servants even stop upstairs to get their fix of Botox when the nurse is in.

But when Elliot’s middle-aged daughter, Jodi (Idina Menzel), shows up at his home unexpectedly, damaged and in a full, self-destructive free fall after losing her husband to a younger woman, she must reckon with the reality that her aging father has been living with a youthful pleasure of his own — a chiseled, erotic boy-toy named Trey (Will Brittain), the same age as his college-bound grandson.

Looking for the warmth of family to ground her in crisis, Jodi instead steps inside a pulsing world of vanity, a hedonic playpen where she must confront the nature of love, lust and family.

It’s an odd little play, for sure. Bound not by some eccentric plot — and to be clear, there really is no plot outside of the nuclear reactions of all those confined to this pressure-cooker space (and the general arc of any standard comedy) — “Skintight” turns on Harmon’s expectations of the human eye.

Seething with homoeroticism — namely between Jodi’s early-20s son, Benji (Eli Gelb), and grandfather’s boy-toy, Trey — and intensely comedic as Harmon exploits the sheer narcissism of his creations, “Skintight” hinges on the human eye’s instinct for voyeurism, on our inevitable desire to take a peek, to stare at something we know we shouldn’t.

As the Isaac family descends on the patriarch’s home, each harboring their own resentments and attractions, Harmon makes clear that this play’s lessons lie not in big, dramatic gestures of plot and form; instead, “Skintight’s” marrow sits in the unsaid tensions between his characters, boiling just below the skin, and in our own desires to ogle others for their attractiveness and to look back at ourselves in a narcissistic expectation of our own beauty.

It’s an exercise in which all of his characters participate and in which his audience is expected to engage just the same, as all before them broil beneath their own, self-made image.

So too does Harmon take the homoerotic to task. Elliot Isaac is old, and his boy-toy (a term ripe for unpacking itself) is purposely young, purposefully beautiful and purposefully used for sex.

“And here he stands, at 20,” says Elliot to Jodi, defending his choice in a man to his baffled daughter, “just on the other side of it all, still dripping with the aftermath of having been made into something. From the heartland. Cornfed. Who knows what cornfed even means, but the word is enough to just about stop my heart. Your mother and I made you almost fifty years ago; seven years ago, this boy had never even cum.”

If Harmon seeks to probe the utility of beauty, so too does he look to trace the edges of the gay aesthetic, of sex and beauty in gay culture.

“I wake up,” he continues, “and the first thing I see is him. Lying next to me. I touch him. I touch his skin, that skin, stretched like a crisp, freshly-ironed sheet pulled tight across a perfectly made bed; creaseless; and all you want is to slip inside those sheets and stay there forever.”

And thus, teetering on the hot fumes of its characters’ vanity, “Skintight” necessarily rides on the back of perfect performance — and its cast, shepherded by careful (and comedic) direction from Daniel Aukin (“Admissions”), takes Harmon’s demands to task.

Idina Menzel, under a good deal of pressure as audiences arrive to see how the beloved Broadway diva reckons with her first straight play, triumphs. As Jodi — a middle-aged mother striving to make a connection with her child and a woman not in some slow descent into despair, but in an utter implosion, altogether unable to stop the hemorrhaging as she falls apart on stage — the seasoned actress gives an incredibly real, incredibly believable performance. Menzel constructs someone we all know, someone who is instantly recognizable.

As boy-toy Trey, Will Brittain (“Everybody Wants Some!!”) gives not just a brilliantly funny performance, but one that succeeds in injecting a character made to be purposefully vacant with complexity.

Ultimately, “Skintight” will leave you with more questions than answers. It’s persistent inquiry into each of its characters superficiality, scene after scene as the Isaac family discuss their own frustrations with how others see them and how they see others, as they argue over who can count as family and who can not, makes “Skintight” feel nearly like a debate play. Bound by no plot, it’s a meditation more than a story.

Harmon’s writing hung in my head long into my dinner after the show, and I suspect it will  others’. Over food, I talked for some time with my dinner date about what we had seen, about a central question of Harmon’s script: is beauty and vanity utterly American and is it an American exercise to worship either? And, over wine, as all good plays do, it lived on far past its curtain.