Here’s the thing about Vogue: You don’t read it once. You read it as often as you please, cover to cover, including the ads, and you still don’t learn the secret of fashion.

And that’s what director R.J. Cutler’s Vogue documentary, “The September Issue,” is like. It’s delicious and ensnaring and easy on the eyes, but it can’t give you the definitive truth about notoriously frosty Vogue editor Anna Wintour.

That isn’t Cutler’s fault. Wintour is, after all, hardly the kind of gal whose je ne sais quoi can be neatly lassoed in 90 minutes worth of documentary film.

Cutler’s crew spent months filming Wintour (previously fictionalized onscreen in “The Devil Wears Prada”) and her familiars as they prepared for the September 2007 Vogue, the largest-ever issue of the iconic women’s glossy. Although “The September Issue” (a Cannes hit) could surely have tapped into any number of story lines, Cutler wisely chose to spin just a few well-developed yarns as he tracked the Vogue team’s travels from Paris to Rome to the magazine’s Manhattan war rooms.

Slowly coaxing out addictive strains of human drama, the chicly understated documentary zeroes in on a principal cast – Wintour, Vogue creative director Grace Coddington, a few big-name designers and photogs, Wintour’s daughter (Bee Shaffer), assorted silent thin ladies, insufferably obsequious design editor Charlie Churchward (who resigned in 2008) and cape-wearing correspondent André Leon Talley, whom we see playing tennis in a vintage diamond watch, his Louis Vuitton racket case tossed to the sidelines.

Bypassing most of the hectic magazine-making itself, “The September Issue” shows us Wintour in more revealing situations – among friends, or at least among intimates, smack in the calmish eye of the haute couture storm. Eschewing narration and other impositions, the film gracefully sticks to its cinema verite approach, allowing the Vogue clan to open up (as much as its members will open up) without prodding or commentary.

Of course, we really want to know about Wintour – and what we learn is that she, although a diminutive blonde in a floral day dress, can reduce a room full of gents to near-tears. But the real heroine here is Coddington, 68, the fiercely endearing Welsh-born ex-model who (like the London-born Wintour, 59) has done battle at Vogue for decades.

It’s Coddington – the only “September Issue” subject who deigns to talk to the documentary cameraman (cinematographer Robert Richman) assigned to follow her – who’s responsible for Vogue’s imaginative, lush editorial spreads and soft color palette (an aesthetic that “The September Issue” rather cleverly echoes). And it’s Coddington alone who talks back to Wintour, allowing the film to focus on the interesting, occasionally risible tussle between Coddington-and-her-Art and Wintour-and-her-Commercial-Savvy.

An addictive, sly fox of a film, “The September Issue” proffers a clearer, although still inevitably obscured view of the massive Vogue world. Whether or not you give two shakes of a rat’s bum about fashion, the documentary offers compelling insight into a tiny elite world that typically operates behind closed doors. But for those who give two shakes and then some about Wintour & Co., those doors can never, sadly, be opened wide enough.