WHAT IT’S ABOUT This is the story of the late Riley B. King, better known as bluesman B.B. King, who rose from the son of sharecroppers to one of the most celebrated musicians in the world. Producer-director Jon Brewer seeks to tell most of the story in King’s own words in interviews conducted over several decades until his death last year. Brewer uses King collaborators like Eric Clapton and Bono, as well as those who were influenced by him, from Keith Richards and Ringo Starr to John Mayer and Carlos Santana, to fill in some context, while narrator Morgan Freeman fills in the rest.

MY SAY For fans of King, there aren’t a lot of surprises in “The Life of Riley.” His story has been told well and often by the man himself. That said, the montage of how many musicians could tell that King was playing a particular song, from just one note and his singular vibrato, was a tribute to his skill.

The montage of world leaders, including popes and presidents, was a tribute to King’s importance, culminating, of course, with his duet with President Barack Obama on “Sweet Home Chicago.”

Bono paid tribute to King’s legendary work ethic — King once played 365 shows in a year — saying, “The dude sits down when he’s playing, but he is running through the year.”

And the U2 singer also discussed what it was like to perform with him, adding that King told the band that he really didn’t play chords very often.

“It was a joy to share the stage with B.B. King,” Bono said. “He’s a lesson in grace.”

And really that’s actually what “The Life of Riley” was lacking: King’s grace.

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Almost anyone lucky enough to meet the blues legend comes away with a sense of his sweetness. King, especially before his health began to falter in connection with his diabetes, always seemed to radiate kindness and warmth. Though his songs like “The Thrill Is Gone” radiate the pain and suffering of the blues, his personality offstage couldn’t have been sunnier.

Glimpses of that rare grace would have give people a better idea of what “The Life of Riley” was really like.

BOTTOM LINE A worthy documentation of an extraordinary life.