Like all of Chuck Palahniuk’s novels, “Choke” is about several things, all of them perversely brilliant, few of them discussable in polite company. A Palahniuk book (“Fight Club” is his most famous) is like a slap in the face that makes you laugh and cringe, and maybe it arouses you, too. So why does the movie version of “Choke” feel so … well, tame?

‘Tis the story of one Victor Mancini (Sam Rockwell), a sex addict who’s been making a halfhearted effort to curb his appetites by going to a support group, though he often winds up just meeting kinky new partners there. (“These people are the reason emergency rooms have special tools,” he tells us in the narration.)

Victor works as a re-enactor at a colonial village tourist attraction, something else he does halfheartedly, with his Seth Rogen-ish buddy, Denny (Brad William Henke), who’s also a sex addict, albeit one whose particular compulsion doesn’t require a partner, if you know what I mean. Victor has to work long hours to pay the bills at the nursing home his mother lives in (“For loony broads of all ages, but mostly where grannies get dumped”), which is run by extortionist nuns. His mother, Ida (Anjelica Huston), has a number of delusions and doesn’t recognize Victor anymore. Flashbacks to his childhood show them living life on the run, with his con-artist mother frequently “rescuing” him from his foster homes and taking him on adventures.

In his spare time, Victor makes himself choke in restaurants. Why? Because then a good Samaritan has to perform the Heimlich and save his life, which makes the bystander feel like a hero. It also makes him or her feel like a guardian angel to Victor, and they send him birthday cards and money. You save someone’s life, you feel like their protector forever after. Victor has dozens of these heroes corresponding with him, sending the occasional checks when he mentions needing dental work or something.

Victor’s problem, as you might have surmised, is that he cannot deal with true intimacy. The random sexual encounters and the staged interactions with life-saving strangers are the closest he can get to real love. His inability to love (or be loved) becomes a problem when he develops a crush on one of his mother’s doctors, Paige Marshall (Kelly Macdonald). She’s willing to have sex with him (for reasons I won’t spoil for you), but he finds he can’t perform. He actually likes her. The story gets crazier from there, with Ida’s diary (written in Italian) and the identity of Victor’s father coming into play as he looks for answers about who he is and why he’s so messed up.

The film was adapted and directed by Clark Gregg (who also plays Victor’s colonial village boss), and it was clearly a labor of love for him. Though he’s a familiar actor, Gregg has never directed anything before, much less tried to write a screenplay based on a bizarre, outlandish novel. Several of Palahniuk’s books have been declared “unfilmable,” and while “Choke” is one of his more straightforward efforts, it’s still awfully hard to capture its edgy lunacy.

Gregg’s movie version almost overlooks the restaurant-choking scam entirely (a little odd, considering it’s where the title comes from), and the story’s jaw-dropping climax — which involves Victor’s intestinal tract — is drastically underplayed. The film comes off as funny, yes, but it never really gels into the madcap lark that it ought to be. How can a movie about a colonial-reenacting sex addict feel so normal?

My hat’s off to Sam Rockwell for giving another game performance, though. His career is marked by roles like this one: freewheeling yet grounded in reality, and almost always funny. He deserves a starring role in a major box-office hit. “Choke” probably won’t be it, and the movie is not the distillation of Palahniuk’s genius that it should be. But for fans of Rockwell and fans of Palahniuk, it’ll tide us over until that blessed day arrives.

B- (1 hr., 29 min.; R, a lot of nudity and strong sexuality, abundant harsh profanity and vulgar dialogue.)