The new rock documentary “Mistaken for Strangers” is alternately hilarious, cringe-inducing, inspiring, depressing, stupid and profoundly intelligent.

Fans looking to learn something about The National will find that this baffling guerrilla-style film is only tangentially about the Brooklyn quintet. Instead, it’s a curiously engaging story about family, missed opportunities, achievement, second chances and, ultimately, love.

The documentary is directed by Tom Berninger, brother to The National’s lead singer, Matt. The band is made up of two sets of brothers — multi-instrumentalists Bryce and Aaron Dessner and rhythm section Scott and Bryan Devendorf — and Matt Berninger saw a kind of symmetry in hiring Tom onto the road crew during The National’s “High Violet” world tour. Tom, an amateur filmmaker, decides to bring his handheld camera along.

Turns out Tom and Matt are complete opposites.

The film’s most difficult — and honest — moments come when Tom asks his parents to explain why Matt has so much success where he has none.

You may not learn much about The National, and that will no doubt turn off some viewers. But you learn something about love and family. Not your average rock doc.