10/28/2014 05:41 pm ET Updated Dec 28, 2014

I'll Be Me: The Long Farewell of Glen Campbell

Viewing I'll Be Me is akin to watching a tightrope act -- breathtakingly exhilarating -- but also agitating, as one fears for the fall.

James Keach's film is more of a document than a documentary. In many truly great documentaries there is a twist, an unexpected element of surprise, often a revelation that things are not exactly how they have seemed from the start of the story. That is not provided in I'll Be Me, as we know from the start that he has been suffering from Alzheimer's Disease.

When young, Campbell appeared as if a god, with his good looks, brilliant guitar playing and an achingly beautiful singing voice. But his archetype is more like a god from a Norse legend. He is one of a flawed group of super-beings, in that he reached great heights, followed by equally powerful lows. His numerous wives and children and his bouts of substance abuse are touched upon in I'll Be Me, but barely.

For the first half, this beautifully filmed piece is excitingly paced, but things start to unravel toward the middle, with the Alzheimer's becoming the star of the show. There were also many extraneous political musings -- from Nancy Pelosi to John Boehner.

Campbell, not only musically talented, but slyly witty, often claims that he only remembers what he needs to when confronted by his doctors and wife, Kim. But they almost seem to be hectoring him, with their constant questions and his wife's overly candid discussion of his intimate desires and bathroom habits. TMI.

To give credit where it is due, Campbell has claimed that he found sobriety with his wife and certainly has had three lovely and talented children with her. But she does seem to have an agenda as she beams at him beatifically and claims that his alcohol addiction was caused by his need to forget his past family woes. That piece of pop-phycology ignores the research indicating that addiction is a disease that causes such problems, not visa-versa. It is also clear this Kim is running this show.

There is much exciting music, the highlight being Campbell's stunning performance on The Tonight Show (with Jay Leno), coordinated with the public recognition of his impending decline.

Sadly, as the tour proceeds, we are witness to a man's disintegration on the stage -- the proceedings being palatable only because of Glen's humor, still glowing voice and musicianship. There are moments of brilliance, especially in his New York Town Hall performance of Jimmy Webb's "The Moon's a Harsh Mistress." But the movie presents more slip-ups then necessary to make its point.

Campbell's life is much more complex and interesting than this film could ever hope to cover. His eldest daughter, Debby, writes that she was unceremoniously fired from the touring band. She also calls to task how Glen has been treated since the end of a grueling tour. Her book, Life With my Father Glen Campbell, a cry from her heart, offers another side of the story presented on the screen.

Hopefully, a more balanced and informative portrayal of Glen's life and music will be put together in the future, in the style of PBS's American Masters. For that is ultimately what Glen is, first and foremost, an iconic yet, very human character, with a great capacity to make the audience fall in love -- hard and forever.

However flawed this film may be -- one thing is truly indisputable: It was good to spend so much time with the ever-fascinating Glen Campbell, a shining star who will always remain "Gentle on My Mind."