They've embedded themselves into popular culture, so much so that the words "Mad Max" are used in the media as shorthand to describe a dystopian future. Which is handy because "Mad Max" fits in a headline much more easily than "dystopian".

One of the key parallels between the two franchises is that they both have obsessive fans who feel compelled to dress up as their favourite character. Obsessive adult fans.

While - even though I rate the Mad Max films quite highly - I would be fine in making fun of grown-ups who want to spent hundreds of dollars on a costume so they can play pretend, this documentary about the Mad Max phenomenon rarely does.

Rather, it shows them as people with a passion for the movies, people who have managed to memorise every line of dialogue, who travel from all over the place to attend reunions full of people just like them.

And they are all around the world - Mad Max has made rabid fans of people in the US, Europe and Japan, among other places.

On the surface, it seems odd that shy, reclusive types become popular and successful musicians.

I mean, they have to stand up on a stage in front of people and perform their songs - which is the complete opposite of shy and/or reclusive.

But there is sense behind this apparent conflict.

Often, the shy types turn to music to express themselves, to get stuff out, to find solace or comfort.

Locked up in their bedrooms, it's pretty much all about them using songwriting and playing as a release valve for whatever they need to get out.

Then, gradually, they play a song for someone, get a good response and then slowly start exposing their songs to others.

If the songs are good enough, they find themselves on big stages performing these often deeply personal songs in front of loads of people.

They find themselves the source of worship, and have to talk to the music media almost constantly, trying to bat away the journo's efforts to dig beneath the surface to find something the musician really doesn't want to share.

It also seems odd that a reclusive musician would agree to make a documentary. One in which she's asked by the film-maker to keep an audio diary, knowing some of those recordings will end up in the film.

That's the situation we're in with Courtney Barnett and her doco Anonymous Club.

It's much more than a straight-forward rock doco, where there is plenty of onstage footage, mixed in with backstage antics showing how much fun the rock and roll life is.

While there is onstage footage of Barnett here, by around the halfway mark it takes a left turn. We find her talking about the alienation and depression she feels and whether she really wants to keep doing this.

I'm not sure why she choose to open up and be so candid - but I'm glad she did. It makes for a compelling documentary, and one that might cause people to realise a life in the rock and roll spotlight isn't all it's cracked up to be.