The film: What you expect from James Mangold's look at the life of the late country music great Johnny Cash will greatly affect what you take away from it. If you're after real insights or revelations about the man in black, don't bother. If you want a quick look at his love affair with June Carter that dominated his life, look no further.

And this works both for and against the film. When Mangold treads tried and true musicians' biopic territory, you can almost sense the filmmaker running down his list. Early childhood marred by family tragedy? Check. Finds outlet for emotions through music? Check. Wily music producer urges him to play the music that's 'in his heart'? Check. Battle with drugs and booze? Check. Long-suffering wife? Check. It plays like a highlight reel.

Thankfully, Joaquin Phoenix puts in a smouldering, scene-stealing performance as Cash, full of pent-up fury. And it's when the singer's heart is melted by Reese Witherspoon - who won an Oscar for her role as Carter - that the film finally takes off. Given screen time together, Phoenix and Witherspoon (below) bring the production alive, finding the real sense of the passion that fuelled a sometimes volatile relationship.

As a love story, then, the film has its charms. But things never go further than skin deep. This is movie-making for the matinees.

Much was made in the pre-release publicity about the leads providing their own vocals for the soundtrack - and there are some cracking re-enactments of live per-formances, too, none better than Cash's triumphant show at Folsom Prison - whereas the cartoon-like cameos of Elvis (Tyler Hilton) and Jerry Lee Lewis (Waylon Malloy Payne) are best forgotten.

Again, Mangold skirts around what might be really interesting: who, actually, were these people? We get the fights, the love, the lust.

That's all well and good for a while, but you don't come away from the film feeling that you really know anything new about Cash (who was, by all reports, a complicated - and often contradictory - piece of work) or about Carter. And that's a great shame.

The extras: The two-disc edition is jammed with bonuses, including two featurettes - one on the prison concert and what was going on behind the scenes, and one that thankfully digs deeper into the couple's relationship - and a few extra numbers from the stars.

June Carter gets a chance to tell her tale in the making-of documentary, which also comes with Cash anecdotes from the likes of friends and contemporaries Willie Nelson and Kris Kristofferson, and - for reasons that remain unexplained - Kid Rock. The first disc also provides the obligatory director's commentary and deleted scenes.

The verdict: Filmmaking by numbers.