Whatever version of his story you chose to believe, and there will probably never be one that can be agreed on, Richard Kuklinski was one scary son of a bitch. Prior to his arrest in 1986, he probably killed more than 100 people, maybe as many as 250. One at a time, starting at the age of 14. He only turned pro years later; before getting work with New Jersey mobsters, he dealt with his inner demons by killing random vagrants in the seedier areas of Manhattan, knowing that the police were unlikely to waste too much time investigating.

Kuklinski talked a lot after he was jailed, up until his death (possibly at mob hands) in 2006. He reminisced on camera for an HBO series in 2001, and has been the subject of several books. I read one of them a few years ago, Philip Carlo’s The Ice Man: Confessions of a Mafia Contract Killer. At least, I read as much of it as I could: Some parts I had to skip over, especially the ones dealing with the hits where he was paid to make sure the victim suffered before he died. (Don’t even ask about the cave with the rats.)

The Iceman is based on a different book about Kuklinski; plans to film Carlo’s book with Mickey Rourke have apparently fallen through, and that may be just as well. Even if, as some in the know charge, some of Kuklinski’s tales are unlikely at best, they’re too horrible for film.

Still, this version co-written and directed by Ariel Vromen veers rather too far in the opposite direction. It’s worth seeing simply because Vromen cast Michael Shannon as Kuklinski, and I can think of no contemporary actor better able to portray both monstrousness and pathos. You just can’t take your eyes off him, even when you want to.

Vromen’s film centers on an apparent incongruity in Kuklinski’s life, that for most of his adult life he lived in the suburbs as a devoted family man, with a wife (Winona Ryder) and two daughters. I don’t think most viewers will be too shocked by that possibility, even though Vromen adjusts the story to emphasize it. The worst thing is that in doing so he downplays the most compelling parts of Kuklinski’s awful story, the careful attention to detail that allowed him to evade detection for so long. When he was arrested on specific charges, the FBI had no idea that a single man was responsible for so many other unsolved murders.

On its own, The Iceman is a moderately grim crime story, a pale echo of Goodfellas made watchable by an oddly impressive cast—one wonders how Vromen got the likes of James Franco, Ray Liotta, Chris Evans, and David Schwimmer to appear in such a low-budget film. And for many viewers, the fact that it isn’t a fraction as nasty as it might have been is probably a plus.

Watch the trailer for The Iceman