Another solid music documentary, this one no concert film but an unnerving study of a troubled soul celebrated by many for his talents as a singer-songwriter. Daniel Johnston is revered by cultists as an artist of extraordinary gifts, but he’s also a person who descended into severe mental illness after a precocious boyhood as cartoonist, amateur filmmaker and musician. Using what appears to be an ocean of film footage and audio tapes made by Johnston recording his early years, as well as found footage from the later period and interviews with friends, family members and people who have tried (and usually failed) to collaborate with him, director Jeff Feuerzeig has assembled a remarkably detailed and incisive overview of his curious rise and fall, the almost reverential attitude many have toward his talent and the reality of the life to which he’s come.

The “public” side of Johnston’s fractured “career,”such as it was, is covered perfectly well in the film (he found his way from Virginia to Austin, Texas, where he took a job sweeping up at a local MacDonalds, incessantly hawked his homemade cassettes, got onstage, won fans and even made it onto MTV before descending into full-blown manic depression, drug use and religious paranoia, and even during stays in mental institutions he was courted by record companies).

But where “The Devil and Daniel Johnston” shines is on the personal side. Not in terms of his own experiences and inner life, which the documentary can’t really penetrate, but with respect to how his pain is reflected in that of those close to him who have been affected by his swings and depressions. At some remove there’s Laurie Allen, a fellow student whom Johnston became obsessed with as a romantic ideal when he was briefly in college (at the time when his illness really began to manifest itself); she remains an almost enigmatic presence, talked about rather than talking for herself, but she was and is his muse. And the ex-manager who continues to peddle the recordings unasked and unpaid out of a fanatical belief in Johnston’s genius. And especially Johnston’s parents Bill and Mabel, the church-going, straight-arrow couple uncomprehending of their gangly boy’s unconventional interests (and sometimes portrayed by the the young rebel in the most unflattering terms) and now, late in life, ministering to their pudgy, middle-aged son as best they can, worrying about what will happen to him after they’re gone. The film is affecting in its portrait of Johnston, but it’s the tale of his parents that’s truly heartbreaking.

One aspect of “The Devil and Daniel Johnston” that doesn’t quite work is its treatment of his music. Despite the remarks offered by his devotees–many of them well-known figures–it’s not easy to regard the fragments we actually hear as being evidence of genius unless one comes to the movie with that idea already in mind. But one can’t expect a two-hour documentary to do everything, and what Feuerzeig’s film does concentrate on, it does very well. It might not convince you that Daniel Johnston is a great artist, but it does persuade you that he’s a fascinating case study.