The latest from Project X director Nima Nourizadeh is the definition of a one-joke movie. To be fair, though, this is August. Most movies dumped into the dog-days disposal system fail to offer even that much entertainment. Good luck making it out of the multiplex with your frontal lobe intact after sitting through something like Hitman: Agent 47. April may be the cruelest month, but August is the dumbest.

Considered in that context, American Ultra is a pretty pleasant surprise. Its lone joke is a fairly funny one. Jesse Eisenberg plays a West Virginia stoner who discovers, to his shock, that he's a sleeper agent trained and brainwashed by the CIA.

Of course, the joke isn't that Mike Howell can't remember his past. Netflix probably has an algorithm devoted exclusively to directing customers to pictures with that premise. No, the joke is that he's a baked Jason Bourne. The director and writer Max Landis have consciously crafted their film as an homage to the Bourne series, appropriating key plot points and character types while giving them stoner-comedy tweaks. The name of the sleepy town where Mike lives? Liman. As in Doug, the creator of the Bourne franchise.

As the movie opens, Mike is living happily with his girlfriend, Phoebe, played by Kristen Stewart. While she embraces his slacker lifestyle, she's clearly the more adult of the two. "We're the perfect fucked-up couple," he declares. "You're perfect, and I'm the fuckup."

One night Mike is sitting at the register of the mini-mart where he works, spooning up instant ramen, when he notices a couple of shadowy figures doing something to his car. An instant later, they're lying in pools of blood; Mike has dispatched them in the blink of an eye, using his spoon and sizzling noodles as deadly weapons. Turns out his thing is killing people with ordinary items like a dustpan, frozen burger, skillet — whatever's handy.

What would a Bourne homage be without a high-ranking spook back at Langley plotting the former agent's elimination? That would be careerist Adrian Yates (Topher Grace, channeling David Strathairn). There's no good reason to terminate Mike. It's just the kind of black op that makes the Bourne world go round, keeping everything and everyone in bullet-blasting motion. Connie Britton stands in for Joan Allen, playing a character who risks her life to reactivate Mike and give him a fighting chance.

Nourizadeh gives his hero lots of chances to fight, and he proves adept at staging the action in ways that prove simultaneously amusing and graphically violent. The second act lags, though, as Mike perturbs Yates by wiping out wave after wave of attackers. Once you understand someone's an unstoppable killing machine, watching him not be stopped can lose its charm.

Things pick up in the final act with an imaginatively choreographed confrontation between Mike and a literal truckload of assassins. They should've called it Operation Overkill. Yates makes the mistake of letting this fight take place in a big-box home-goods store, where the tool and kitchen departments alone supply Mike with everything he needs to even the odds. The sequence is delightfully over the top in a way that's reminiscent of the church massacre scene in Kingsman: The Secret Service.

So, yeah, for August, you could do far worse. Eisenberg lends impressive depth to his character in places — and hey, who ever imagined the day would come when we'd see him sporting hair extensions and doing the action hero thing? Now what would really be funny is if they made a sequel to American Ultra and replaced the busy Eisenberg with Jeremy Renner.