In his last years, Gore Vidal flawlessly played the role of elder statesman-as-curmudgeon; director Nicholas Wrathall’s documentary captures him in fighting form — witty, incisive, and coolly dismissive of his foes and lessers. His elegantly low-key dis of the late Christopher Hitchens at a book signing is masterful bitchiness. Immensely enjoyable from its wistful opening (Vidal leaning on a cane, standing over the burial plot he planned to share with longtime partner Howard Austen, who died in 2003), the film’s strength is the way it uses Vidal’s life (illustrated in vintage photos, newsreels, home movies, and title cards stamped with his epigrammatic sayings) to catalog 20th-century America’s sweeping political, cultural, and social changes. Interviewed in the sprawling, nearly packed up Italian home he shared with Austen, the elderly Vidal pays tribute to some family (his grandfather), eviscerates others (his mother; JFK), and disembowels prepackaged patriotism and contemporary conventional wisdom on queer identity. Wrathall lays out news clips of iconic interview moments across the decades: “The whole point to a ruling class,” he says with mild exasperation to one TV host, “is that they don’t conspire, they all think alike unless you get out, which is what I did. I defected.” And his withering dismissal of a conservative talking head in the ’60s might come as close as possible to a sound-bite summation of Vidal’s political and philosophical stance. After the man yammers that homosexuality is an assault on core American values, Vidal — a blueblood class traitor — retorts, “Why not begin by saying that our basic values are wrong?” It’s an admittedly hagiographic film, an unabashed celebration of the man and his work and worldview. The few mild naysayers are largely set up to be knocked down, but as such the film is invigorating.