Kenneth Tynan was famous and successful by his mid-twenties, a London and later New York theater critic whose passionate, eloquent, lacerating judgments influenced the course of the form in the 1950s. In his 30s, he reinvented himself, taking a gig as literary manager of London’s National Theatre to which its director, Sir Laurence Olivier, personally invited him—to shut him up, some say. By his 40s, Tynan’s life was a titillating wreck of ill health (emphysema didn’t stop him from chain-smoking), debt, kinky extramarital dalliances, alcoholism, and occupational and existential malaise. He was only 53 when he died in 1980.

How thrilling to discover that a theater critic could lead a rock star’s life! Tynan even caused a national scandal by saying “fuck” on TV, 30 years before Bono did it. That was in ’65, the year of Rubber Soul and Thunderball and “Satisfaction,” but still half a decade before he began keeping the diaries that were finally published in 2001. To see Tynan, a 95-minute monologue culled from those private musings, is to form an idea why his widow, the writer Kathleen Tynan, declined to release them during her lifetime—before your seat is warm, even. (She wrote her own biography of him anyway, publishing it seven years after his death.)

Gossip-tickled, sex-drenched, and seasoned by the occasional observation about socialism—or worse, theater—the diaries have given adapters Richard Nelson and Colin Chambers ample material to sustain our prurient interest as actor Philip Goodwin talks us through the often desperate final decade of Tynan’s life. Performing on a bare stage save for a single chair, Goodwin rolls his subject’s florid, lurid recollections around in his mouth for maximum comic effect. Tynan was a stammerer, and Goodwin subtly includes this impediment in his performance, though it presumably didn’t afflict the writer when committing his interior thoughts to paper.

Though some of this critic among critics’ crit—ah, detractors have pegged his alleged desire for the approbation of his famous subjects as a fatal flaw, Nelson and Chambers don’t give us much in the way of gossip. It’s fun to hear, for example, about how Anthony Hopkins stepped into the role of Coriolanus after Christopher Plummer was fired for publicly berating the director and refusing to apologize. But those kernels of stage lore are vastly outnumbered and out-whatevered by Tynan’s explications of his lifelong obsession with spanking and the human anus, which, buyer beware, he expounds upon with the same fearless, clinical fluency with which he expounded upon everything. If Nelson and Chambers (or perhaps New Yorker theater critic John Lahr, who edited Tynan’s journals for publication) are to be trusted, Tynan just wrote about assholes a lot. Hey, you don’t need to be a critic of Tynan’s rare acuity to understand this much: People like what they like. And a critic ought to say so when the things that people like are full of shit.

Lest the point get lost, this is a good show. Reviewing the diaries in London’s Observer upon their publication in 2001, David Hare remarked that they “achieve power as a kind of protracted, agonising note before death, sometimes almost too painful to read, the record of a man who is, like a Russian hero, losing faith at an inexplicably early age in the ability of the world to sustain his interest.”

That plaintive quality gradually makes its presence felt onstage. Goodwin and director Paul Mullins let us delight in their subject’s rapier turns of phrase while experiencing a tightening sense of fatalism. “Feel that God is making his point with rather vulgar overstatement,’’ he says, describing a genital injury that has left him mostly impotent. The Tynan we’ve by then been rooked into thinking we know would never buy in to that notion of Puritanical payback, but to pass up a good line really would run contrary to his religion. His words entrance us long after they’d ceased to do the same for him.