The advance word on U2's current world tour was that we were in for a treat, but only if our idea of fun was to see the biggest band in existence fall flat on their faces. American articles gloated about slow- selling tickets, cancelled concerts, an ill- conceived stage set, and a band who spent more time trimming their moustaches than rehearsing. Having seen Bono and co at Wembley Stadium, I can reassure anyone going to the Edinburgh show that there's no need to worry, and I can warn the vultures that they may go hungry. It's official: the PopMart tour is no disaster.

Think about it. The whole travelling circus consists of 52 trucks and 15 buses moving 200 personnel and 1,200 tonnes of equipment to 62 cities. With an investment as colossal as that, it's not likely that the band are going to stagger on half an hour late and forget which key "Pride" is in, however much we may rub our hands together at the prospect. Organisations as big as this never offer you the sadistic glee of witnessing something truly awful. It just doesn't happen, except maybe where Michael Jackson is concerned.

Stretching across most of one end of the stadium was the largest video screen ever built, 833 square yards of it, with pixels the size of car headlamps. It flashed like sheet lightning, and the four musicians pumped up "Mofo" into the brutal, bruising monster of a track it was intended to be on the album. Tidal waves of beats flooded the stadium. The Edge skimmed glimmering notes over the top. In this environment, U2's sweeping songs make sense. This is the environment they were written for.

After that, though, it was up-and-downhill all the way. The long concert sagged under the weight of incessant drum loops and tune-deficient songs, and was only just buoyed up by the gimmickry of a 35-foot high lemon-shaped, motorised mirrorball and a catwalk which let Bono promenade through the adoring masses. In the 1990s stadium-rock stakes, U2 fall behind Tina Turner and the Rolling Stones and even earlier incarnations of U2 themselves. But as I said, fans needn't worry unduly. If you're going to the show you'll see a job well done: feel free to skip a few paragraphs to where the words "Reading Festival" appear in bold print. If, on the other hand, you harbour doubts about U2, read on.

In the interviews the group gave when Pop (Island) was released, you couldn't get from one paragraph to another without tripping over the words "kitsch", "trashy" and "irony". The theme was taken up by the album's gaudy packaging and the tacky video for the first single, "Discotheque". Listen to the album itself, however, and you start to wonder whether all this talk of irony was ironic. Pop is not a pop record. It's as kitsch and trashy as an oak tree. It's not about pop culture or postmodernism or McDonald's-led global homogenisation. It's a survey of Bono's crises - spiritual, identity, midlife - articulated in the same vague, portentous terms that the band's devotees love and their detractors hate. U2 haven't reinvented themselves, they've had a respray.

As with Pop, so with PopMart. The eponymous theme is everywhere: there are animated Lichtensteins on the screen and there's a Piccadilly Circus of neon; there's a 100-foot-high arch (designed, it seemed, to obscure the screen behind it) and there's that mirror-citrus (hence the inflatable lemons being sold on the T-shirt stands). The costumes qualify as kitsch, too. Bono takes the stage in a boxer's robe, throwing punches at the air. The Edge is in his now-familiar guise of the cowboy from the Village People, and Adam Clayton, the bassist, is in his now-familiar guise of something or other involving an orange boiler suit. Edge provides some kitsch pop levity, however self- conscious, by singing "Suspicious Minds" to a karaoke-machine backing, and then quietly gets on with the job of being a genius, slicing the air with echoing guitar chimes.

But Bono ... Bono is having problems. He wants to be a cyberpunk rock'n'roll star, but he can't stop being a chin-stroking, flag-waving tortured artist. He wants to dress up in wacky clothes, just as long as people don't forget that he is every bit as serious and earnest as he ever was. The ironic disguise keeps slipping, giving us embarrassing flashes of a puffed-up little fellow prone to messianic gestures and grating, faux-humble comments ("It's an amazing place to play, especially being Irish, 'n'all"). He might be more comfortable if he threw away the goggles and the top printed with an Action Man's torso, and if he dug his vests and long black coats out of the wardrobe.

There's not enough room here to review the individual bands who played at last weekend's Reading Festival, but that's no loss. The headliners - Suede, Manic Street Preachers and Metallica - have all been dragging around their current albums for too long already, so there was no unmissable, feverishly anticipated highlight to match those of recent years: the long- awaited return of Bjork or Hole, say, or the long-awaited retirement of the Stone Roses.

Reading is recognised as the grand finale of the festival season, but now that it's preceded by Phoenix and T in the Park and V97, it feels more like the curtain call - the morning after instead of the last-night party. With so many newcomers competing for their share of bands and enthusiasm, Reading's slot at the end of the summer is no longer quite so enviable.

It needs to distinguish itself from its rivals, and maybe the solution would be for it to become an all-out greaser's convention, as it used to be. It's taken a step in that direction already. On Sunday, the main stage came over all heavy metal, with the aforementioned Metallica joined by Marilyn Manson, Terrorvision and Bush, and the sad effect being that the weekend was turned from one long Glastonbury-style jamboree into two separate festivals. Well, almost separate. If bearded blokes in Megadeth T-shirts can queue for the same baked-potato stalls as glitter-faced teenagers in Placebo T-shirts, then world peace may not be an impossible dream.

U2: Edinburgh Murrayfield Stadium (0131 557 6969), Tues.