"Dahmer" tries to tell one of the most horrific stories of recent years. But the whole story of Jeffrey Dahmer does not get told in this movie. There are some shocking moments, but most of the movie gets bogged down in flashbacks (and even flashbacks-within-flashbacks). At some points, you cannot tell if you're watching another flashback or the present moment in the story.
The performances are good all-around. Jeremy Renner does an incredible job at playing Dahmer, expressing a laundry list of emotions with his face and body language alone.I think you'll find it dull if you are looking for blood and gore but Dahmer wasn't one of those kind of killers, he killed for company, not blood lust.