Mamma mia, here we go again: one Abba revival wasn’t enough, so the popular musical based on the Swedish band’s hits is back for another go-round. Having played a successful run in 2001 (when it opened three weeks before September 11), Mamma Mia! is returning to the Colonial Theatre for another three months — synthesizers, white spandex, and all.

History remembers Abba’s music as 100 percent fluff, but that isn’t really fair: at worst, it was only about 85 percent fluff. Bubblegummy at first, the group found some emotional depth when the two marriages started breaking up: next to the high-gloss pop now being peddled by Britney Spears and Shania Twain, later Abba hits like " Knowing Me, Knowing You " seem downright profound. Many of Abba’s big numbers already sounded like show tunes; the rest sounded like either disco ( " Dancing Queen " ) or ’60s girl-group pop.

Now defunct for more than two decades, the group have sworn never to reunite. So Mamma Mia!’s producers (who include Abba member and songwriter Björn Ulvaeus) have done the next best thing: they’ve wrapped a story around 22 of Abba’s hits and key album tracks, the same songs the group would likely play if they were to get back together. (Although it’s not actually in the show, " Waterloo " is saved for the final encore.) A keyboard-heavy band re-create the original arrangements — more closely, in fact, than Abba did on their one live album. And lead actresses Dee Hoty and Michelle Aravena suggest the torchy styles of Abba singers Agnetha Faltskog and Anna-Frid Lyngstad while speaking considerably better English (for most of their career, the Abba women sang phonetically).

There is also a plot, more or less — but the story is so old-fashioned, it’s a wonder it comes from writer Catherine Johnson, a British fringe-theater veteran and former punk. On the eve of her wedding, sweet and innocent Sophie Sheridan (Aravena) discovers an old diary kept by mother Donna (Hoty) and learns that mom was having flings with three different men at the time she was conceived. Longing to know her real father’s identity, she invites all three to her wedding, on a Greek island where Donna now runs a hotel. It turns out, however, that Donna isn’t quite that much a free spirit: she was merely rebounding when the first of her flings — American architect Sam (Gary P. Lynch), her one true love — went back to his fiancée, from whom he’s now long divorced.

Once you know that much, you can see the rest of the plot coming a mile up Boylston Street. So the second act’s shift to a more dramatic tone doesn’t quite work, especially since the lovers’ big confrontation takes place over the song " S.O.S. " (lines like " It used to be so nice, it used to be so good " aren’t quite the stuff of dramatic revelation). But the book livens things up by giving Donna a pair of bohemian friends, feminist writer Rosie (Gabrielle Jones) and thrice-married socialite Tanya (Mary Ellen Mahoney).

Thanks to Hoty’s performance, Donna emerges as the one three-dimensional character. Tough, wounded, and doggedly romantic, she’s the perfect Abba heroine, and she turns " The Winner Takes It All " into the second-act showstopper it was always meant to be. It’s strange, though, that the main characters in Mamma Mia! are nearly all heterosexual women. As anyone who’s been to Provincetown or seen The Adventures of Priscilla: Queen of the Desert can attest, that’s not the demographic that’s kept Abba in the pop consciousness all these years.

The other problem is that the show is so glaringly unsexy — this is disco-era music, after all. From the looks of things, Donna has been celibate since her wild weekend two decades earlier; she gets stuck wearing overalls for half the show. Abba’s two most brazen tunes, " Voulez-Vous " and " Gimme Gimme Gimme (A Man After Midnight), " both turn up during a semi-slapstick, squeaky-clean bachelor-party montage. Even the requisite camp is muted: the spandex jumpsuits get hauled out only when Donna, Rosie, and Tanya reunite their old singing group on " Super Trouper, " a scene more poignant than celebratory.

But if the details are often wrong, the spirit of Mamma Mia! is just about right. The program doesn’t list the songs in the order they appear, so you have fun guessing how Johnson is going to work each one into the story line. ( " Take a Chance on Me " is the one real surprise; there are no awards for figuring out when " I Do, I Do, I Do, I Do " makes its appearance.) Even with the songs outweighing the story, Mamma Mia! comes out looking unfashionably wistful, sentimental, and romantic. Just the way Abba did in the ’70s.