“Life Itself” has its Madison premiere at 3 p.m. Saturday at the Union South Marquee Theatre, 1208 W. Dayton St., as part of the UW-Cinematheque summer series. PG-13, 2:03, three and a half stars out of four. FREE!

“For me, the movies are like a machine that generates empathy.” — Roger Ebert

Roger Ebert was a great film writer for many reasons, but one of them was that he wasn’t just a great film writer, just writing about movies when he was writing about movies. Read through his reviews, and you’ll find political arguments, philosophical musings, remembrances of his boyhood in Champaign-Urbana. He believed that the beauty and the power of a great movie didn’t stop at the concession stand, but extended out the front doors into — life itself.

Steve James’ wonderful documentary “Life Itself” is based on Ebert’s memoir of the same name, but expands beyond it. It manages the difficult trick of being both an autobiography (often told in Ebert’s words from the book, brought to life by an uncanny voice actor) and a biography. It gives us insight into his earliest days as a college reporter and his final days in the hospital just before he died last April. It’s a love letter to Ebert from his friends and his fans, but it’s also as tough on the man as he was on the movies — as tough as he was on himself.

So we learn how Ebert hit the ground running as a writer, penning eloquently furious editorials for the Daily Illini during the civil rights movement that surpassed what was being written about in the national press: “The blood is on so many hands, that history will weep in the telling. And it is not new blood. It is old blood. And as Lady MacBeth learned. It will never wash away.” A 21-year-old college student wrote that.

But we also learn that, as a hotshot young Chicago Sun-Times movie reviewer in the ’60s and ’70s, he was a alcoholic and something of a blowhard. He told great stories, but didn’t always like to share the stage. His taste in women was suspect. “He was nice, but not that nice,” a friend remembers of Ebert’s long nights on the barstool. Lest you think “Life Itself” is telling tales out of school, Ebert put this is in the book, too. He took his last drink in 1978.

Colleagues and filmmakers attest to the influence of his plainspoken writing; he talked about difficult movies in a way that made mainstream movies want to see them, and he talked about mainstream hits in a way that found hidden depths where others only saw the shallows. He championed little films he believed in throughout his career — UW grad Errol Morris talks about how his 1978 documentary “Gates of Heaven” was released in the middle of a New York theater strike, seemingly dooming its chances at the box office. Ebert and Gene Siskel reviewed Morris’ film on “Sneak Previews” — three times. “I don’t think I’d have a career if not for those guys,” Morris says now.

We get a lot of juicy backstage info on the rivalry between Ebert and Siskel, and see some of the duo’s truly epic onscreen throwdowns, such as a memorable bout over “Benji the Hunted.” Both could be petulant, both could be insecure and arrogant, but the friendship that lay beneath that rivalry grew over the years. “He’s an asshole,” Siskel once told his wife. “But he’s my asshole.”

James could have made a hagiography of Ebert (after all, Ebert went to bat in a big way for James’ “Hoop Dreams” 20 years ago), but seemed to know that such an approach wouldn’t have sat well with Ebert. James began filming Ebert in December 2012, and it’s painful to watch the once-gregarious man in what would be the last five months of his life, the lower half of his face just a flap of skin, unable to eat or speak, struggling through physical therapy in evident pain.

But he also delights in the company of his family and friends, communicating through voice-recognition software on his laptop, smiles, or, of course, that trademarked thumbs-up. If the film can be tough on Roger, it is properly loving towards his wife Chaz, and the unflagging tenderness and courage she showed him. The scene where Chaz describes the day Ebert died, holding hands in a hospital room with family, is devastating.

And during those last few years, Ebert unquestionably did the best writing of his life, not just his movie reviews but a torrent of blog posts, some of which formed the foundation of “Life Itself.” Where other journalist raised on print feared the digital age, the veteran newspaperman found himself liberated by the Internet and the possibilities it offered a writer.

Ebert inspired legions of movie writers and movie fans throughout his life. But it’s how he faced his last few years — with dignity, humor and grace — that should inspire everybody.