“Savages” is a tightly wound and vastly entertaining pulp thriller — it’s perhaps director Oliver Stone’s strongest work since “Nixon” (1995). Freed from the burden of having to say something “important” — a burden that deflated his Sept. 11 drama “World Trade Center” (2006) and prevented his George Bush biopic “W.” (2008) from reaching potentially ecstatic heights — Stone gets back to what he does best, mixing brash showmanship with gleeful provocation.

At least until the tacked-on happy ending.

“Savages” doesn’t have the moral imagination and emotional reach of his greatest works, such as “Born on the Fourth of July” (1989), “JFK” (1991) and “Wall Street” (1987), but it’s propelled by the same half-crazed energy and purposefulness. This director is never better than when he’s rooting at our rawest societal nerves.

Based on Don Winslow’s 2010 novel, the film hearkens back to those 1980s, Stone-scripted efforts like “8 Million Ways To Die” and “Scarface,” movies about the sinister allure of hard drugs and big money. In Laguna Beach, Calif., the short-tempered war veteran Chon (Taylor Kitsch) and his do-gooder, Berkeley-grad best buddy Ben (Aaron Johnson) have become low-level drug kingpins, cultivating a higher-class brand of pot with seeds from Afghanistan. Chon and Ben live an idyllic life with the beautiful Ophelia (Blake Lively), O for short, whom they both share as a girlfriend, mostly insulated from the seedier aspects of the drug trade.

The opening section of “Savages” moves with bullet speed, complete with rapid-fire edited flashbacks and a pair of fairly graphic sex scenes. Stone takes particular delight in the gym-toned, sun-bronzed bodies of his three leads; the movie — as its title suggests — is about how we’re all savages at heart, motivated by sex, food and illicit stimulation, and willing to get brutally violent when our sanctity is threatened. And when a powerful Mexican cartel reaches out to Chon and Ben, eager to become business partners — things turn very violent indeed.

One of the smartest things about the screenplay adaptation (by Stone, Winslow and Shane Salerno) is that, even as it posits a fantasy scenario of wealthy white kids running up against Mexican cartels, it doesn’t flinch from the realities of a war on drugs that’s beset by corruption and unimaginable cruelty. The cartel is run by Elena (Salma Hayek), a purring diva in Tijuana not above ordering the beheadings of those who have crossed her. Her chief henchmen in the United States are Alex (Demian Bichir) and Lado (the always good Benicio Del Toro), who orchestrate the kidnapping of O, at which point Elena issues Ben and Chon an ultimatum: Join us, or her head gets cut off next. Caught in the middle of all this is the DEA agent Dennis (John Travolta), who’s on the take from more than one source, and who would be willing to sell anyone out to the highest bidder.

A lesser filmmaker might have been content to set this enjoyably convoluted story in motion, and sit back and watch the sparks fly. Stone turns it into a fascinating story of generational divide and spiritual malaise in the early 21st century. Played nicely by Lively, Johnson and especially Kitsch, the three younger characters embody a very distinct, Gen-Y conundrum: They want to be able to live on their own terms without also having to reckon with the brutalities of the modern world. The older characters, meanwhile, are all hustlers: They’ve got kids they’re trying to put through college, families they’re trying to protect. Despite the millions of dollars at stake, they’re basically just trudging along with the rest of us.

For nearly two hours, Stone keeps a tight grip on the material, providing plenty of space for his ensemble cast to deftly chew the scenery: Del Toro mumbles and mutters and keeps petting his own mustache, as if some tiny cat settled onto his face. Travolta keeps in perpetual motion, talking a mile a minute. Hayek, in a long Cleopatra wig and one gorgeous outfit after another, combines the imperiousness of Bette Davis circa “All About Eve” with the sort of exaggerated vulnerability you usually only find on telenovelas; in a word, she’s inspired.

It’s only in the final stretch that the movie stumbles, when Stone serves up one ending and then doubles back and serves up another. The first ending is right out of the novel, and had he cut himself off there, Stone might have given us one of the most powerful nihilistic visions of a world turned upside down since his own “Natural Born Killers.” Instead, he opts for an unconvincing, let’s-tie-up-all-the-bows coda — a sop to the Hollywood bean counters and a betrayal of everything that’s comes before it.

Make no mistake, even with that botched finale, “Savages” is eminently worth seeing.

Check out of the theater five minutes before it actually ends, though, and you may think you’ve witnessed the best American movie of the year.