“When I’m bad, I’m so, so bad,” Donna Summer sang in “Last Dance,” and that perfectly describes the new Broadway musical about her life.

“Summer,” which opened Monday, is borderline incoherent. It turns a complex woman’s life into a hagiography, a slide show of events — Boston childhood, stint in Europe, fame, motherhood, illness — minus context or emotion.

Three women play her at different points in her life, which they narrate like Bible passages. Storm Lever’s Duckling Donna, Ariana DeBose’s Disco Donna and LaChanze’s Diva Donna are excellent, especially DeBose (late of “Hamilton”), and they sing the heck out of “MacArthur Park,” “I Feel Love,” “On the Radio” and more. Trouble is, they also play the woman’s mother, friends and sisters. Keeping track of the double casting is a struggle.

You’d think the songs would redeem this show. Summer sang some of the best dance music of all time, and 23 classic numbers are jammed into less than two hours. But some of the tunes here — including a rendition of “No More Tears” Summer belts out while being beaten by her German ex — are hard to enjoy.

Des McAnuff, who gives us more ups and downs than a heart monitor, directed this mess. Remarkably, he’s the same man who made a hit out of “Jersey Boys.” This time he seems to have Scotch-taped together some wonky ideas, such as having women play producers David Geffen and Giorgio Moroder. That might have been fine if McAnuff actually committed to it, but Casablanca Records president Neil Bogart is played by a dude, as are Summer’s lovers, so whatever point McAnuff was trying to make is lost.

For a show that openly encourages theatergoers to stand up and dance, their only real opportunity to do so comes at the end and lasts all of three minutes. Before then, we get some awkward business about the anti-gay remarks Summer reportedly made at a 1983 concert. Although she denied she’d said them at the time, many of her most devoted followers were upset. In “Summer,” the singer, who died of lung cancer in 2012, offers an explanation, an apology and a declaration of how much she loves her gay fans. True or not, it’s a cheap moment.

Enough is enough!