Invision/AP 1 / 5

LOS ANGELES (AP) -- Elizabeth Taylor says the new Michael Jackson documentary is "the single most brilliant piece of filmmaking" she has ever seen.

The 77-year-old actress and longtime Jackson friend says she saw "Michael Jackson's This Is It" last week, but was sworn to secrecy until Monday, when she posted her thoughts about the film on Twitter.

Based on rehearsal footage shot while Jackson was preparing for his series of comeback concerts, the movie "cements forever Michael's genius in every aspect of creativity," Taylor says. She urged her fans to see it "again and again."

Jackson died in June at age 50, just before he was to begin a 50-concert run in London.

"Michael Jackson's This Is It" opens worldwide Tuesday night.