“American Assassin” marks Dylan O’Brien’s first leading role in a film aimed at adults. While he’s received praise in the “Maze Runner” movies and MTV’s “Teen Wolf,” his role as Mitch Rapp could launch him in a franchise with an even wider audience. However, judging from the first reviews, critics might not want to see any “American Assassin” sequels.

Based on Vince Flynn’s bestselling novels, the R-rated film follows Mitch Rapp as he goes on a mission for revenge after terrorists kill his fiancée. He joins the CIA and quickly proves he has talent as a killer.

On the bright side, reviewers aren’t panning O’Brien’s performance. Several noted that he was very convincing in the role. Unfortunately, it’s just not a great movie.

“American Assassin” reviews “American Assassin” is not a hit with film critics. Photo: CBS Films

That plot sounded a little too familiar to many critics. Several, including Variety’s Amy Nicholson, noted that the film isn’t particularly original. “Yet ‘American Assassin’ is so close-mouthed and macho that it blends in with Bourne, Bond and ‘Taken’s’ Brian Mills. Rapp can blast his way through Turkey — but this sullen, swollen hero can’t elbow those box office heavyweights to make room,” she wrote.

Nicholson, who is familiar with Flynn’s novels, also disliked the changes from the book. While he had decades to acquire his skill in the novels, Rapp becomes an expert CIA agent in a year and a half in the movie. Aging Rapp down means that he’s “less an intelligence expert than a superhero in jeans. The excess makes him silly.”

The script, written by Stephen Schiff, Michael Finch, Marshall Herskovitz and Ed Zwick, fell flat too. “The screenplay, credited to four accomplished writers, abounds in clichés and jargon that feel tired but probably reflect the bureaucratese of this sphere (‘He’s testing through the roof!’),” the Hollywood Reporter’s Sheri Linden noted.

The Independent’s Geoffrey McNab was actually surprised Michael Keaton took a role in “American Assassin,” especially since Stan, a mentor to Rapp, is such a static character. “It’s dismaying to see an actor as accomplished as Michael Keaton playing someone as dumb, macho and one dimensional as Stan. Keaton just about gets away with it. He plays the role with such manic conviction that we almost believe in the character.”

“American Assassin” movie reviews While the actors deliver fine performances, many reviews noted that the “American Assassin” script was lackluster. Photo: CBS Films

The Wrap’s Todd Gilchrist said O’Brien “oozes charisma,” but he also noted that the movie is just too simple. “If nothing else, perhaps the film would have benefited from embracing its beach-read appeal and playing up the ‘American’ aspect of its celebration of military heroism,” he suggested. “‘Assassin’ wouldn’t have necessarily been a better film because of it, but that feels like an easier (or, let’s say, more commercial) route to get to explore this hero’s journey in future installments with, one would hope, some of the complexity that’s absent here.”

Not everyone thought there was sequel potential, though. Jonathan Pile of Empire panned the movie. “It should be apparent by this point, that ‘American Assassin’ is beyond ludicrous — the type of film where a gunfight in a hotel room that spills out into the corridors yet somehow fails to be noticed by any of the other guests,” he wrote.

Overall, it sounds like you won’t be missing much if you skip this action movie. “American Assassin” hits theaters Sept. 15.