Katy Perry in Paramount Pictures' 2012 "Part of Me." Credit: Paramount Pictures

Release Date: Thursday 7/5

Us Rating: ***

You've got to applaud Katy Perry

In her engrossing 3-D documentary, Katy Perry: Part of Me, (shot during her 2011 world tour), Perry, 27, fully illustrates how she went from ultra-Christian guitar strummer to outspoken pop star.

But candy-colored concert footage aside, the real fireworks go off when the singer reveals a fascinating glimpse into her troubled relationship with Russell Brand.

"I'm trying to keep my marriage alive," a frustrated Perry pleads to the camera as she makes plans to see him in L.A. during a rare day off. (Brand, 36, makes only fleeting cameos, leaving viewers to wonder about his take on their issues.)

The "fairy tale" union ends, of course, but Perry's inspiring story lives on.