If you've never listened to The Magnetic Fields, I'm not sure I'd recommend this documentary. It tracks the origin of The Magnetic Fields by following the life of it's members - namely Stephin Merritt, the cranky but talented lead. Without smiling once throughout the film, you learn how passionate Merritt is about creating music, and how his friendships have enabled that.
It's less a narrative or conflict driven documentary, and more a retelling of the history of the band. If you haven't heard of The Magnetic Fields, go ahead and listen to every album they've put out then watch this.