Many of the documentaries you tend to see at film festivals represent one of two polar extremes. One is the trenchant, heartfelt exploration of some issue of politics -- which, while fascinating, can be a bit of a slog. The other is the breezy, buzzy exploration of some aspect of show business -- which, while fun, can be a bit light. Trumbo -- directed by Peter Askin and based on Christopher Trumbo's play taken from his father Dalton Trumbo's letters -- manages to hit a perfect sweet spot between those two extremes. It's informative, impassioned, insightful; it's funny and fabulous and filled with film-love.

Dalton Trumbo was a novelist and screenwriter -- one of the highest-paid writers in Hollywood -- before the House Un-American Activities Committee came calling. Trumbo's brief time in the Communist Party was motivated by what would come to be called "premature anti-fascism" -- double-speak for not liking Hitler before not liking Hitler was national policy. He was called before Senator Joe McCarthy and the HUAC hearings, and found guilty of contempt of Congress for not naming names. Of his communist past, we hear Trumbo explain that "At its peak, the party had only 80,000 members; that's less than The Elks. And they had a lot more guns." Of his court sentence, he noted "As far as I'm concerned, it was a just verdict; I was in contempt of that congress. ..."

It's a funny line; it gets a lot less funny when you realize that Trumbo in fact served jail time -- and was an unemployable pariah for years after. But Trumbo - which combines interview footage of Trumbo with dramatic readings of his letters rendered by actors like David Strathairn, Joan Allen, Paul Giamatti, Donald Sutherland and Michael Douglas -- pulls off the delicate balancing act of switching between white-hot passion with warm, true good humor. And through the interview footage and the staged readings we get a sense of Trumbo's voice as a writer: His love of language, his fondness for juxtaposition, his use of repetition in structure to lend his work an iron-strong spine. We also get a sense of his voice as a human being: His belief in America, his love for his friends, his hatred for the indifferent souls who allow the betrayers and killers to walk the Earth.