‘Life Is but a Dream,” Beyonce Knowles’s HBO documentary about herself, is billed as a revealing look inside the superstar’s world circa 2011-12, as she shifts business gears, reinjects her music with an updated R&B feel and, as you surely know, gives birth to a daughter. The project is mostly just a fleeting glimpse, which is ultimately a disappointment, given the world’s desperate and ongoing interest in all things Beyonce.

Early in the film, Beyonce relays that special feeling of celebrity futility when it comes to guarding her private life. Like the ultra-famous who came before her, she wishes there were not a market for the news and photographs of things she’d rather not share.

But I don’t know how anyone could make sense of “Life Is but a Dream” without having followed Beyonce’s ­every move and every high note as reported by the multimedia infotainment sphere. You must come to this program knowing the basic trajectory of her career thus far; you must already know that she relieved her father of his managerial duties; you must know she has a husband who, it seems, is also a famous performer. You must know all about the envelope-pushing album we see her recording in the studio. It would help greatly if you could discern the importance of a tirelessly rehearsed awards-show performance (that, if you’re a fan, you will have already seen when it aired) and be able to tell how it is different from all the Beyonce performances that came before it.

Beyonce is a talker, but she’s not much of an explainer; she never tells us where we’re going or who people are, or what everyone is doing at a particular moment. She never even tells us the name of her baby, when, near the end of the film, she lets the camera linger briefly as she cuddles and nuzzles it.

“Life Is but a Dream” has no through-line, no linear narrative. It’s more like a hallucinatory advertisement for success, and to her credit Beyonce put the word “dream” in the title. The theme is celebrity ennui alternating with spiritual and emotional fulfillment. Which isn’t much of a theme. The film obeys the only structure available to anyone who has plenty of footage, but no story — collage.

Thus, home videos from the 1990s of her Houston girlhood are swirled into the singer’s endless, present-day trips through back hallways, into and out of elevators, then into tinted-window SUVs, then aboard helicopters and private jets that deliver her to yet another series of hallways and rehearsal spaces and dressing rooms, all of this leading to her most comfortable space, which is the high-wattage concert stage.

We are given the impression that many of Beyonce’s best and most honest conversations happen with her computer, where she keeps a video journal of her emotions. “I want to be able to sing about how much I hate myself if that’s how I feel,” she tells her laptop in a moment of artistic declaration. “I’m feeling very empty because of my relationship with my dad,” she says, in another whisper. “I feel like my soul has been tarnished.” About managing her career on her own, she says: “I don’t care if I don’t sell one record. [This decision] is bigger than my career.”

I don’t believe that for a second, but this brand of confessional plays strong and sounds assertive, and that’s something Beyonce sells by the truckload.

The other thing she sells — her sensational stage performances — is vividly captured throughout “Life Is but a Dream,” which is filled with hot concert footage. I would have liked to learn more about the special screen effects that her technicians designed for her live act (which were put to stunning use at her recent Super Bowl halftime show), but this is a movie that doesn’t tell you much of anything you’d really want to know.

Beyonce: Life Isbut a Dream

(90 minutes) airs Saturday
at 9 p.m. on HBO.