Plenty of movie stars break out and then spend the rest of their careers in high profile commercial fare, more concerned with their popularity and the movement of product than the art of performing. Dwayne Johnson, for all his likeability (and talent), is a classic example, seemingly more interested in being a movie star than an actor. Schwarzenegger and Stallone built entire careers on it even though the latter had some acting talent, and it's been a tried and true career path in Hollywood for aeons.

Some stars go the other way. They seem to want to become actors to express and stretch themselves, to see where the art form can take them, to tell genuine stories that mean something to them and collect awards along the way, the low quality but supernova-like phenomenon that launched their careers having served its purpose but shunted to the bottom of their ouvre like a slightly embarrasing family member.

As I write this review, Kirsten Stewart is rumoured to be signing up for another remake of Charlie's Angels, probably filling her bank account enough to pay off a new house in Beverly Hills but flushing away all the credibility she's garnered with Camp X-Ray, The Clouds of Sils Maria, Café Society and Still Alice.

Viggo Mortensen, after conquering Hollywood with his portrayal of Aragorn in the Lord of the Rings trilogy, has followed a similar path to Stewart's until now, appearing mostly in dramatic indies like The Road, A Dangerous Method and A History of Violence. And with Captain Fantastic, there's no such commercial sell-out like Charlie's Angels on the horizon.

He plays Ben, a father to a clutch of kids who live an isolated life in America's forested Pacific northwest. Unlike the sullen, uneducated and inarticulate teenagers he and his children spend time with later in the film, his kids can hunt and feed themselves, they can read and critique literature, they can survive in the wilderness and they can quote (and understand the intent of) the Bill of Rights while they're still toddlers. On the surface, Ben and his family seem to have the perfect life.

But the kids' mother is in hospital for a mental illness, and when she takes her own life Ben has no choice but to take his kids into the wider world. Her parents Jack (Frank Langella) and Abagail (Ann Dowd) have never agreed with the choices their daughter and son in law took to raise their family, and see Ben's isolating of his kids from the wider world as child abuse no matter how smart or capable they are.

When they forbid Ben from attending his own wife's funeral the whole gang hits the road to crash it. For many of the kids it's the first time they've seen the outside world at all. For some of the older ones like Bodevan (George MacKay) it's the first time they really engage with it, in his case meeting a pretty young teenage girl in a trailer park they're stopping at and realising that for all the stuff he knows, he knows nothing about anything so simple as talking to girls.

Another of Ben's sons, Nai (Charlie Shotwell) is even more disillusioned with the life his father has provided for him – not least because he's nursing a broken hand from a rock climbing incident from before they set out – and he's the one most tempted by his grandparents' encouragement to leave his monastic life and stay with them, turning on his father in the process.

The family reconnects ('collides' is the more accurate term) not just with their dead mothers' parents but their in laws, Dave (Steve Zahn), Harper (Kathryn Hahn) and their aforementioned typical teenagers along the way, and the movie skillfully and ruefully highlights the schisms between the two worlds and the tension that arises when the kids are fully exposed to them.

Writer/director Matt Ross is also clever enough not to come down on one side or the other. Ben isn't made a single minded survivalist loony and Jack isn't just a hateful old man who disagrees with him. Both have their points of view and neither are wrong, they just don't align.

The film has an incredible cast, the young stars are as great as the adult actors and it has some interesting things to say about whether to (and how much to) connect with society if you don't like its ideals as well as tell a good story about interesting people.

The only problem is the absolutely terrible title. While Ross might have intended for it to say something about Ben, it sounds like something they came up with the night before they started shooting, and I wish someone had done market research of some sort about people who heard about it and avoided it because they thought it was a Marvel movie.