The cast of "Fun Home," with music by Jeanine Tesori,...

The cast of "Fun Home," with music by Jeanine Tesori, book and Lyrics by Lisa Kron, based on the Alison Bechdel book and directed by Sam Gold, running at The Public Theater at Astor Place. Credit: Joan Marcus

It seems awfully early in the season to make such a declaration, but here goes. The Public Theater is the most exciting, most challenging, most surprising theater in New York. At least it is right now, and that strikes me as worth acknowledging.

A couple of weekends ago, I found myself having three very different terrific times in three of the five action-packed theaters in the sprawling 19th century building, once the Astor Library, that Joseph Papp famously bought from the city in 1967 for a dollar. I've been going back so often lately that I've considered pitching a tent.

In fact, perhaps for the first time since the irreplaceable visionary died in 1990, the entire place has a vibrancy -- I hate the word but, OK, a vibe -- that permeated the place in Papp's heyday. The East Village landmark, smartly renovated recently for $40 million, has a bright new lobby and a big, welcoming stretch of stairs out front.

Most important, of course, is the work that artistic director Oskar Eustis produces inside. When friends asked me what to see this fall, I recommended they buy into the Public's audience-friendly subscription series. Even before anything opened, the lineup looked enticing. Thus far, it has more than fulfilled that promise.

Eustis, who has had downs as well as ups since he took over the institution in 2005, doesn't try to conceal his pleasure at the season so far. "Things are going OK," he says, joking at the understatement. "Right now, why shouldn't I feel cheerful?" Why, indeed?

"Fun Home," the important and wonderful musical developed by Lisa Kron and Jeanine Tesori at the Public Lab, has Broadway producers jostling one another for a transfer. Wallace Shawn's brilliantly upsetting and weird "Grasses of a Thousand Colors" continues the worthy tribute to Shawn and director André Gregory.

Eustis has given a new home to the Foundry Theatre's joyful yet uncompromising staging of Bertolt Brecht's "Good Person of Szechwan," a hit last season at La Mama. And if the rest of Richard Nelson's unfolding four-play cycle, "The Apple Family: Scenes From Life in the Country," is as excellent as the two I saw the past two Saturdays, this is going to be a very big and significant work.

"Arguendo," which closed its scheduled run late last month, was an imaginative commentary on the Supreme Court's 1991 case regarding exotic dancers by the Elevator Repair Service -- the company responsible for last season's staggering "Gatz," a word-for-word marathon staging of "The Great Gatsby."

Meanwhile, Joe's Pub, the essential cabaret created by former artistic director George C. Wolfe, is packed with innovation nightly. Eustis' season began at the pub with 29 nightly monologues by the fascinating, controversial Mike Daisey. Public Forums, an unusually provocative lecture-and-reading series begun under Eustis, brings in the likes of MSNBC commentator Rachel Maddow, Pulitzer-winning economist Joseph Stiglitz and Tony Kushner -- whose masterwork "Angels in America" was commissioned by Eustis when he ran the Eureka Theatre in San Francisco.

Oh, and "Here Lies Love," David Byrne's environmental hit musical from last season, awaits transfer to a suitable freewheeling space and not, as previously rumored, to a traditional Broadway playhouse. "We're not going to bring it back unless we find a space that moves the show forward," vows Eustis, despite its acclaim and box-office success. "We'll make it better than it was at the Public, or we're not going to do it."

Wolfe, the powerful, delightfully subversive, creative vortex of the Public since 1993, announced his resignation in 2004. At that time, the Public and its five theaters were considered too costly and unwieldy to run, too small to make sense in a modern economy. Unlike during Papp's time, there was too much competition from other theaters.

The Public, everyone agreed, was a beast to run, even without the summers of free Shakespeare in Central Park. When Wolfe left, the whole complex had a $12 million budget, shockingly small compared with the $14 million Papp had in 1990.

Eustis has not just run the monster, but expanded it. His current budget is $28 million. "I don't know if I'd say I proved anything," he says when I press him to explain the success. "I realize that the Public's business model is defiantly swimming upstream" against commercial pressures on nonprofit theaters.

He certainly hasn't been untouched by such unsuccessful Broadway transfers as "Bloody Bloody Andrew Jackson." But he says the Public is now "capable of attracting philanthropic support that's much healthier" than the commercial system. "When one of our shows doesn't work, it has negligible impact on our economic bottom line."

Not everything, to his mind, is perfect. Before I could even ask about the limited ethnic diversity in the season, he jumps in to say, "I look at this fall, and the only thing wrong is that it's too white. We're going to correct that in the spring" with, for starters, Suzan-Lori Parks' "Father Comes Home From the Wars (Parts 1, 2 & 3)" and writer-director Tarell Alvin McCraney's stripped-down, radical new version of Shakespeare's "Antony & Cleopatra."

"And we're going to massively correct that next year," he vows, adding that this fall "is not a full expression of our mission."

That mission, so far, includes the Mobile Shakespeare Unit, a reinvention of the free touring project that Papp began in 1957. A production of "Much Ado About Nothing" has been touring the city's jails and shelters, then moves into the Public Nov. 25 for a brief run -- at $20 a seat. The Lab, which also charges $20 a ticket, "is our attempt to make a lot of cheaper shows, stripped down." Not just "Fun Home," but "Bloody Bloody" and the "Apple Family Plays" were created in the Lab.

And he says he is especially "intoxicated" by a production of "The Tempest" that ran briefly in Central Park last fall, performed by 230 nonprofessionals. "This was a total success that had nothing to do with commercial theater."

If Eustis can sound evangelical, consider that his belief in "theater as a social force" grows directly from Papp. "Joe was fantastically creative," he says, marveling about the impresario who made history with nontraditional casting, plays about AIDS and Vietnam, not to mention such breakthroughs as "Hair" and "A Chorus Line."

"But he wasn't the greatest stabilizer. Before I leave here, I want this place to be in a position where nobody can question that it's going to continue into the future."

I asked what he most would like to tell Papp about his achievements. "This isn't an achievement yet," he says after a long pause. "But I hope he would be proud of my goal not to change one whit of his vision and mission."

Even after an autumn like this one, Eustis won't relax enough to boast.

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