“He was going to be dead by 30, so after that he was on borrowed time.” So graphic artist Ralph Steadman summarizes the strange and wonderful life journey of Hunter S. Thompson, a “complex walking monument to misbehavior” and one of the most influential writers of the 20th century. Thompson’s life and times are chronicled in this exhaustive documentary that follows the writer’s “lower-middle-class” childhood in Louisville as the son of a single mother librarian to his early years as a starving freelancer (his first wife, Sondi Wright, describes how they lived on “elk liver, milk and salad” for longer than anyone should be expected to) to his life- and career-changing ride with the Hell’s Angels, an assignment that saw Thompson’s knack for “participatory journalism” make way for what would become his trademark “gonzo” style. Gonzo is perhaps a bit too comprehensive with a 118-minute running time that eventually feels rather oppressive, but the film succeeds in painting a fascinating portrait of a one-of-a-kind artist and human being, one whom fellow writer Tom Wolfe compared to Mark Twain in both style and personality. Even Thompson’s “political enemies” recall him fondly, with former President Jimmy Carter grinning at how Hunter loved to “rock the boat” and Pat Buchanan cracking a smile as he remembers how Thompson described him as a “half-crazed Davy Crockett running around the parapets of Nixon’s Alamo.” Narrated by — who else? — Fear and Loathing in Las Vegas star Johnny Depp, who predictably (and perhaps a bit tediously) indulges his own Hunter imitation as he reads excerpts from his various books.