It helps to not know a lot, but to know just enough, about Lawless going in. To that end, I'll be sort of vague here. (Plus I often find it tedious when reviews spend half their time recapping the plot.)
A violent Prohibition-era drama about bootleggers, Lawless is scripted by Nick Cave (which explains the prominence of the bleak music) based on a historical novel, which is itself based on real characters and events.
If it wasn't for that key point, I'd have found the movie (especially the climax) much more dull than I did, and much more derivative of Scorcese's crime films. I mean this thing is so Scorcese-esque that it's positively Scorcesian.
I'm also happy to say that I've now finally seen Tom Hardy, who's clearly an excellent performer, in a movie that wasn't a near-total waste of time. (That's a disparaging comment directed at Star Trek: Nemesis and The Dark Knight Rises—total wastes of time—and the new Tinker Tailor, just near-total.) His character here is a real delight—sort of a more brutal Jamie Hyneman.
Don't be discouraged by the top billing of Shia LeBouaeuiuhwhhphf. He's well-suited to the role and he does a fine job. It's the story and structure that are alternately bizarre and predictable.
Perhaps the major thing I disliked about Lawless was its emptiness. I'm not sure how else to put it. Certainly that's partly because Prohibition eventually ends, and all those bootleggers must have been like, "Man, worst anticlimax ever." But there's more to it than that. Lawless is a good slice-of-life look at what things were like back then, but I found it hard to get very invested in the events depicted. Maybe the foreshadowing was too obvious and over-the-top; maybe the tone was so Scorcesian that I expected Scorcesian escalation and didn't really get it.
Viewing it as if it were an unintentional (and for all I know, kind of inaccurate) documentary, though, I found I had enough interest to stay with it to the end. Of course, I'm a slight history nerd—I mean, I almost made it through Barry Lyndon, even.
Fair warning: there's like Reservoir Dogs levels of brutal, bloody violence. There's also boobs. If your kid has one of those edgy history teachers, he (and they do seem to all be dudes, don't they?) will probably show this, assuming they even have time to get past the Civil War in between all the preparing for one standardized test or another.
Star Score: 2.5 out of 5