At this writing, My Best Friend’s Wedding seems poised to become the breakout hit of the summer of 1997. Holy counterprogramming, Batman — it looks like audiences have already grown a little weary of dinosaur attacks, mad bombers, and Nic Cage with his shirt off. Funny thing is, while it seems like My Best Friend’s Wedding could hardly be further from Batman & Robin on the summer movies spectrum, it’s interesting to compare the two. While Gotham City is “dark” by default, My Best Friend’s Wedding suffers from an unconvincing sunniness. B&R has more lame one-liners than you can count, while MBFW is overwhelmingly bland and every bit as silly. In its defense, I should note that MBFW didn’t cost as much as B&R, and doesn’t make nearly as much noise. Choose your poison, gentle reader — it’s just that time of year.

Beautifully photographed by journeyman cinematographer Laszlo Kovacs, My Best Friend’s Wedding goes down easily enough, although the early scenes rely on Julia Roberts’ skills as a comedienne and are thus dangerously insubstantial. As our story opens, we learn that Julianne Potter (Roberts) and a fellow named Michael O’Neal (Dermot Mulroney) are longtime friends — and onetime lovers. The love affair was broken off, but the friendship has endured. And, at one of those silly moments that may be familiar to young lovers, they promised one another that if neither of them had walked down the aisle by the age of 28, the two of them would be married after all.

On the verge of her 28th birthday, Jules gets a phone call that she assumes is a desperate Michael eager to cash in his matrimonial chips. But when she rings him back for a chat, she falls out of the bed — he’s calling to ask her to come to Chicago, where he’s marrying the lovely, wealthy Kimmy Wallace (Cameron Diaz, who makes a pretty but otherwise unremarkable bride). Naturally, it’s only now that Julianne realizes how much Michael has meant to her all these years. Overcome by jealousy, she flies to Chicago with malicious intentions — she wants to break up the happy couple and make Michael realize that she, not Kimmy, is the one for him.

Too bad for the movie that it’s hard ever to identify with Julianne’s singlemindedly selfish quest. Instead, she just seems to be in denial from square one — Roberts is actually playing one of the thickest characters in American movies so far this year. You just want to yell at the screen: “Get a grip!” Roberts looks better than she has in years — accordingly, one scene has her standing around in her underwear — but her performance is so flat you wish somebody would jab her in the ass just to get a rise out of her.

As her beloved Michael, Dermot Mulroney has a face that’s about as expressive as a leather glove and a voice to match. Better she should ditch this loser for her handsome friend George — as played by Rupert Everett (Cemetery Man), he’s a sight for sore eyes. Of all the cast members, Everett is the one consummate professional, and when he joins the party briefly in Chicago, he coaxes both Roberts and Diaz to giddy heights — with Mulroney consigned, thankfully, to watch from the sidelines.

Unfortunately for Jules, George is gay. Ever the sensible counselor, he urges Jules to simply confess her abiding love for Michael. Instead, Jules winds up introducing George as her fiance in a desperate bid to make Michael as jelaous of George as she is of Kimmy. Appalled, he decides to get back at her by hamming it up — groping her in the back of a cab and doing lewd things with his tongue — in hysterical fashion. As George fabricates the details of an impossible affair, this romantic comedy soars — until it crashes and burns with a self-consciously “spontaneous” singalong of “I Say a Little Prayer.” (I’ve never seen the director’s previous Muriel’s Wedding, but I’m told it relied on Abba in the same way this movie relies on Dionne Warwick, Burt Bacharach, and, um, karaoke.) The whole movie’s kind of like that, with a full complement of pretty good ideas ruined by sloppy execution. Fortunately, Everett is back to help sew things up in the closing scenes, adding a touch of much-needed elegance that’s likely to make you remember the movie a little more fondly than it probably deserves.

Screenwriter/producer Ronald Bass also wrote the implausible but winning Dangerous Minds. This film has a similar problem — the actual story can’t make good on the promise of the film’s high concept without flipping our common sense switches. For instance: a key plot contrivance involves Julianne’s unauthorized use of Kimmy’s father’s computer to forge an email message to Michael’s employer. (What she types into the computer is very clearly not an email address at all, but that’s beside the point.) Realizing that what she is about to do is spiteful, destructive, and altogether reprehensible, Julianne decides not to send the email after all. The computer asks her if she wants to “delete” the email or “save it for later.” Exhibiting truly incomprehensible stupidity, Jules quite deliberately decides toleave the forged email on the bride’s father’s computer. I was completely baffled. Why would she do that? Maybe that was actually her computer after all? Does she want to wait until after the wedding and send it then? Does she want the computer’s owner to find the forged email and assume someone else wrote it? Or, deep down inside, does she really want to be found out? The answer is none of the above — it is simply essential to the climax of the film that the email be left on the computer. Surely a movie with a forehead-smacker as big as this one could have made use of a good script doctor. (Maybe Bass the producer nixed the idea on behalf of Bass the writer?)

The real shame is that this is ultimately a screwball comedy that’s decidedly lacking in screwballs — Julianne, Michael, and even Kimmy are all so middle-of-the-road it’s impossible to tell whether any of them would really make a good couple. Other things it’s lacking: witty dialogue, winning performances (with the big exception of Everett, who could easily see this turn into an Oscar nomination), and the stripe of ingenious situational comedy that can turn a shallow character into someone worth caring about. What it’s got going for it is a single gentle lesson on a universal truth — we change, the people we love change, and drifting apart can be painful. Of course, if you’re fully cognizant of all that on the way into the theater, the ending of My Best Friend’s Wedding is simply a foregone conclusion.