‘This Is It’ a fascinating, poignant look at the King of Pop

One thing we know for sure: This isn’t it. The documentary chronicling his final rehearsals ever, “This is It,” isn’t the last we’ll be seeing of the late Michael Jackson. Studios, promoters, his family and many others will continue to exploit his legend and premature passing for money in perpetuity.

The famous perfectionist — a notoriously private master of hype — might have been appalled. Here we spy behind the curtain of his Oz at the master entertainer at age 50 in something less than full-out, peak performance mode. We glimpse a brilliant wizard’s creative process, his command of his craft and his respectful authority over every aspect of an elaborate production during the last four months of his life.

But whatever the ethics of its release, “This” turns out to be a fascinating, tasteful and ultimately poignant presentation of the professional side of the man who first proclaimed himself to be the King of Pop.

He’s bigger than Beethoven? Elvis? Sinatra? Mozart? The Beatles? If you answer “yes,” or even “maybe,” then “This” is a must for you. Devoted Jacksonians will get tingles from every leg twitch, hip gyration and memorable chorus. His trademark bits still reverberate even as they come with inextricable thoughts of an icon’s tragic demise.

Casual fans of the music, exhausted by the post-mortem circus or overwhelmed by the evidence of Jackson’s dark side, can also find nostalgia and uplift in these snippets of backstage-style collaboration and run-through performance — taken from some 120 hours of footage at The Forum and Staples Center in Los Angeles (not originally shot to be a feature film). But they can also just buy the soundtrack of classic hits, in stores now.

Looking thin (even for him) but hardy and in good spirits, Jackson prepares for the sold-out London concert series that would never be. It really might have been the comeback he was hoping for, judging by its massive scale at least. Directed by Kenny Ortega and choreographed by Travis Payne with the star as their czar, the show looked to be a blazing extravaganza. Imaginative mini-movies, pyrotechnics, sets, costumes, and accomplished band musicians and backup singers and dancers combine in service to a pro-love, pro-environment and — most of all — pro-Michael message.

From the opening thumps of “Wanna Be Startin’ Somethin’ ” to a climax of riffing footwork for “Billie Jean,” the set list runs through all or part of about 20 of his most beloved numbers, sometimes with exact moves from the original videos intact.

The magical combo of his evocative voice and graceful hoofing — even if not at complete strength here — reaffirms his artistic greatness. What a talent. What a waste.