It's a paradox that Garrison Keillor, the troubadour of a lost continent of jug bands, roots music, and small-town Americana, is the province of latte-loving public radio. But, as we see in Peter Rosen's Keillor-loving documentary, this unlikely star can also pack them in at county fairs. In a better world, this wholesome humorist would be as popular in our time as Mark Twain or Will Rogers were in theirs; he should be on Late Night rather than the superannuated hipsters we get. Rosen's film faithfully follows Keillor around as he puts on his weekly broadcast and types on a cheap laptop (no Apple product placement here!). Rosen misses the darker Keillor of some of his fiction or the angrier, more politicized Keillor of recent vintage in favor of a sunny look at a nice man, but this is an American Masters production after all. We do get the driven performer who sings sans umbrella in a pouring rain, and that's more than can be said for Twain or Rogers.