Writer Tracy Letts and director William Friedkin proved a formidable combination in their screen version of Letts’s play “Bug” (2007), and the same take-no-prisoners approach characterizes this brutal, violent comedy-drama about a murder-for-hire gone wildly off the rails. “Killer Joe” is a movie that fans of early Tarantino will probably salivate over, but others may find its combination of sex, bloodletting and edgy humor easier to resist.

Another drawback to the film is that, despite Friedkin’s “opening up” of the stage piece—most notably in a chase of a man on foot by cars and motorcycles—the writing remains extremely theatrical. And the sort of speechifying that sounds great, both shocking and oddly poetic, when spoken onstage comes across as highly artificial on screen. Seen live a piece like this, with its flights of verbal dexterity, takes on a weirdly iconic feel, becoming the same sort of mythic reflection of the American psyche as Sam Shepard’s plays so often are. But the spell of such works is too often broken by close-ups and other cinematic devices. (Remember what happened to “Fool for Love” when Robert Altman brought it to the screen?)

Still, “Killer Joe” is intriguing, if you can take the gore and nastiness that earned it the NC-17 rating. Matthew McConaughey continues his career revival with an icily menacing turn as Joe Cooper, a suave Dallas detective whose smooth drawl and perfectly-kept Stetson mask a cold-hearted killer-for-hire. Killer Joe, as he’s known in the trade, is approached by Chris Smith (Emile Hirsch), a nervous young fellow deeply in debt to a drug dealer, about killing his mother, who’s reportedly got a $50,000 life insurance policy that can cover what he owes. But the plan hinges on the agreement of her trailer-trash ex-husband, Chris’ obtuse dad Ansel (Thomas Hayden Church), who lives in a decrepit double-wide with his slutty second wife Sharla (Gina Gershon), a waitress at a pizza parlor with a guy on the side, and Chris’ younger sister Dottie (Juno Temple), a naïve girl with kewpie-doll looks and a distracted air. The policy leaves the benefits totally to Dottie, Chris says, so his dad’s complicity is necessary. It takes little to convince Ansel to go along, though—except for a cut of the proceeds.

The hitch arises when Joe announces he requires a down payment that cash-strapped Chris can’t provide. Happily Joe has already met Dottie, and offers to accept her as a living “retainer.” Chris and Ansel agree to the unusual arrangement. Needless to say, although Joe methodically keeps to his part of the bargain, the Smith side’s part of the plan utterly unravels (literally, in a hilarious scene involving Ansel’s tattered sportscoat), and Dottie—who develops a creepy relationship with Joe—becomes a pawn in a test of wills between the homicidal lawman and Chris, who, it appears, has a more than brotherly interest in his sister. Meanwhile a member of this seedy family is harboring a secret that, when revealed, will unleash an orgy of bloody violence, sexual humiliation and perverse one-upsmanship over a gruesome meal of KFC chicken.

One detects lots of influences at work here—not only the Shepard of “Buried Child” and “Curse of the Starving Class” but the Tennessee Williams of “Baby Doll.” This was Letts’s first play, after all, and dependencies are almost inevitable. But though he’s still working toward his own voice, he’s come up with some moments that are laugh-out-loud funny, others that are grotesquely upsetting and many that just make your skin crawl. Friedkin, as with “Bug,” stages everything for all it’s worth in a gritty, ferocious, no-holds-barred style, and for the most part he’s assembled his cast impeccably. In addition to McConaughey’s pitch-perfect turn, Church proves as successful in capturing Ansel’s animal cunning and survival instinct as he has the character’s apparent obliviousness, and Temple is equally compelling as the shy, virginal girl who may or may not understand what a tease she is. Gershon also strikes paydirt—even if Sharla doesn’t—as Ansel’s money-hungry wife.

But Chris is the spoke of the circular plot, and Hirsch, though a fine young actor, doesn’t manage to express the character’s inner life—his performance is all shouting and exterior effect, and the weakness undermines the overall impact. The few supporting players are also liabilities, making the sequence between Chris and the thugs chasing him—led by Marc Macaulay—almost laughable in an unintended way. Technically, the New Orleans locations are made to look appropriately grubby by ace cinematographer Caleb Deschanel, and the overall production design (by Franco Giacomo-Carbone) certainly gets the seediness down. The result really doesn’t look like Dallas, though, especially given all the scenes set in torrential rain.

“Killer Joe” is definitely not for everyone. You’ll need a strong stomach and a high tolerance for scenes of sexual degradation to endure it, and quite honestly—unlike in Shepard’s best work—the payoff is pretty meager. But there are compensations, not least McConaughey’s mesmerizing performance.