When you think "pop star tour documentary," you probably figure, "OK, there will be a lot of soulless concert footage and a bunch of interviews with the star about how hard it is to be famous, followed by some home video clips and inspirational quotes from their family/friends about how they were destined to be a star from the start." And that's generally what you get.

There's a lot of that stereotypical material in Katy Perry's new tour doc, "Part of Me," but hers has something Justin Bieber's didn't: During her "California Dreams" tour, Perry also was juggling a marriage (to Russell Brand) that would fall apart while she was on the road. The cameras are there not only when Perry's on top of the world, giddily trying on lavish costumes and performing for thousands of avid fans, but also while she's sobbing right before taking the stage in Brazil. It's heartbreaking to watch.

Even if you find Perry's music vapid and candy-coated, the girl watched five singles off the "Teenage Dream" album go to No. 1, which not even the Beatles could say they did. Like Lady Gaga, her slick pop music and kittenish persona appeal to the "weird kids" and the masses alike, so her megastardom can't come as a complete surprise.

"Part of Me" details her rise from Pentecostal childhood to teen gospel singer to behemoth touring machine with pinwheels on her boobs, spliced with 3-D footage from her shows. (In this instance, 3-D is more pleasurable than headache-inducing; you feel like you're in the audience.) It appeals to our voyeuristic nature, giving us plenty of backstage passes to see the naturally pretty Perry turn into a lush, lacquered doll pre-show, sing her heart out and then drag herself to do countless meet-and-greets with fans. She's an old-fashioned workhorse performer, with irresistible charisma.

She is constantly surrounded by Team Katy, a coterie of old friends from her days as a struggling pop star in Los Angeles. Her traveling-minister parents are supportive; her sex appeal is always tongue-in-cheek. Perry says that although her faith has strayed from the strict guidelines of her childhood, she retains a personal relationship with God.

Perry comes across as aggressively likable, especially when she takes off the electric blue wig and gets "real." You root for her. "This tour is my childhood dream ... to wear sparkly costumes and have people listen to me sing," she says.

It's the struggle of career vs. love that is most interesting; Perry makes sure to take "relationship days" during her tour to fly to Brand. It doesn't work out. In the midst of her painful divorce, she watches her sister try on wedding gowns, and the devastation on her face is evident.

"Part of Me" succeeds because it's not afraid to let its big star be vulnerable. Her post-divorce interview feels real. "I'm a romantic. ... I still believe in the fairy tale," Perry says.

That's why it hurts to see Perry standing beneath the stage of her circus tour, trying to pull herself together to perform for a massive São Paulo crowd. You feel Team Katy members in the wings, holding their collective breath as she fights back tears and paints on a smile. For Katy Perry, the show must (and does) go on.

Kara Nesvig is a Minneapolis writer.