In Life Itself, veteran documentarian Steve James adapts Roger Ebert’s memoirs to throw a light on the life of the celebrated Pulitzer Prize-winning movie critic, who died in 2013 following a long battle with thyroid cancer.

Jeremy Kay talks to James about his revealing film, Ebert’s period of dramatic self-discovery, a unique time in film criticism and a remarkable voice actor. Magnolia releases Life Itself in the US on July 4.

How did the movie come about?

It was [executive producer] Steve Zaillian’s idea. He read Roger’s memoir and they reached out to Roger with the idea of it and Roger was intrigued. They reached out to me and I hadn’t read the memoir and fell in love with it and thought it was a great piece of writing. I wouldn’t have done the movie if it had just been about Roger the film critic and parsing his career as a critic and what he contributed.

But the film addresses film criticism

We do get into criticism and we try to give a sense of what made him significant as a critic, but I wanted to get my arms around the whole thing because his memoir does. His life story is the adventure. With respect to critics, it’s funny to think of a critic as having that kind of story because we don’t tend to think of critics as having such interesting lives and yet Roger did that and was one of the most prolific critics.

This is an unusual choice of film for you

I was also interested in the idea of making a biopic of someone whom I admired but who I found complicated and interesting and who was famous. I am known more for cinema verité and following a story over time, which I love, but this was a great opportunity.

There’s a point in the film where Ebert is newly arrived at the Chicago Sun-Times, living large and descending into alcoholism. There’s a sense of self-loathing – why?

I remember someone saying maybe he had reached a dark moment in his life where he felt hopeless about his addiction to alcohol. Roger was a guy who was an only child. His father died young and that was a profound loss to him and Roger was trying to figure out who he was. When he came to Chicago he took on that persona of a newsman. In some ways he was trying on different personas of what person he wanted to be. When you go to the big city you can become a different person and maybe he was speculating that who he’d decided he wanted to be wasn’t really who he wanted to be.

Ultimately he became a beloved critic and broadcaster who brought his love of cinema to the masses. Will we ever see his like again?

Before Roger became this larger-than-life character nobody would have thought he could have happened. You never want to say ‘never’, but there was a confluence of forces that made Roger become what he become and… it’s hard to imagine such a confluence of events happening again. Some of it was fortuitous, some of it was the birth of new American cinema and the rise of a cineaste culture that lauded heavyweight European and Asian directors. And of course there was the TV review show with Gene Siskel.

In later life he took to online writing like a duck to water

I am sure internet criticism would be alive and well without Roger, but because he embraced it so completely when he could no longer speak on TV he helped to make it vibrant. He helped to get internet critics access to screenings.

There are lots of scenes of Ebert in the rehabilitation clinic with his doting wife Chaz. Were there times when you either did not want to film or were blocked from doing so?

I tried to get in to do more filming in the last few weeks and we were rebuffed by doctors. Chaz [pictured with Ebert] tells me Roger was willing to have us come. Towards the end of his life we were all set [for a day’s filming] and I got a call from the PR person from the institution [where Ebert was receiving treatment], saying it was off because the doctors had nixed it.

Part of it was about trying to look out for what was best for him because they’re not a hospital, they’re a rehab institute, so for them to be looking after him was a little scary for them. I had no interest in being there at his bedside when he died and he had no interest in that and neither did Chaz. For all the good Roger’s very public stance on his condition did to inspire others, there’s a moment when it’s all about privacy.

The voice-over of Ebert reading from his memoirs is not the man himself. It’s an astonishing likeness.

That voice-over is from his memoir so they found a voice actor called Stephen Stanton through Chaz’s website. We needed to channel Roger because it’s his writing. Stephen read the memoir and we gave him tapes of Roger to get the cadence of his voice right. In the film it’s clear that it cannot be Roger, but you would be amazed by the number of people who thought it was Roger. To me it is Roger and I wanted to make clear it wasn’t, but I hoped you would forget about it and believe it was Roger.