NEW YORK — Ethan Hawke’s evolution from magnetic movie cub to full-fledged theater lion is now complete, courtesy of his latest foray onto Broadway, as the coarser brother in the mutually destructive rivalry of Sam Shepard’s “True West.”

Hawke proves to be the roaring featured attraction in Roundabout Theatre Company’s revival of Shepard’s 1983 absurdist comedy, directed with a sometimes uncertain grasp on the material by James Macdonald. The play gallops out smartly onto Mimi Lien’s suspiciously cheery suburban kitchen and dining room set, as a fragile truce unravels between Hawke’s burned-out, beer-guzzling slob of a Lee and his preppy, careerist writer-brother, Austin. The younger sibling is played by Paul Dano, an intriguing choice, especially given his recent complex turn as an escape artist in Showtime’s “Escape at Dannemora.”

But the peculiar rhythms of Shepard’s play, a concoction laced with unnatural twists and planted in the satirical soil of a denatured Southwest, lose strength in an under-realized Act 2. As the play unfolds, the intention to make ever clearer that Lee and Austin are cut from the same degenerate cloth, Dano pulls up somewhere short of convincing as a viable match for Lee.

Even so, this “True West,” which had its official opening Thursday at the American Airlines Theatre, has its tickling rewards, particularly in the early going, when the menace in the play is at its most nerve-racking. Lee has invited himself to stay with Austin, a screenwriter at work on what might be his big break, in their mother’s house near the California desert while she’s off on a tour of Alaska.

The evening’s linchpin comic conceit reveals itself in a scene with a film producer (an all-too-mild Gary Wilmes) who is co-opted by Lee into listening to his impromptu pitch for his own (unwritten) screenplay for a western. The witty notion here is that Hollywood tends to look in all the wrong places for authenticity and that Austin and Lee belong to the pioneer spirit of the West about as much as this tacky subdivision, carved out of the Golden State’s gulches and arroyos.

Hawke makes for the kind of childish, out-of-control bully you may remember from your own youth: Austin and Lee themselves revert to the familiar patterns of sibling warfare. With his Yosemite Sam-style facial hair, pit-stained undershirt and a sense of hygiene located somewhere south of revolting, Hawke makes himself the embodiment of unwanted company. As long as it seems Dano’s Austin is engaged in gingerly fending off Lee’s brutish demands, the play feels fully charged.

It’s after the tide turns and the plot’s ironic switcheroo is executed that this “True West” loses its hilariously agitating momentum. By the time that Mom, in the guise of Marylouise Burke, returns from Alaska to find the house a shambles, you may feel as deflated by the denouement as Burke looks.

True West, by Sam Shepard. Directed by James Macdonald. About 2 hours. $59-$352. Through March 17 at American Airlines Theatre, 227 W. 42nd St., New York. 212-719-1300.