First Night: Love Never Dies, Adelphi Theatre, London

At the annual St Giles' Fair in Oxford, there used to a Big Wheel. I could never get enough of this attraction, because here was a magical machine that bore you to the top of its circuit and then gave you a snatched, rapturous view of the dreaming spires (viewed over a college roofscape) just before it made your insides turn a somersault as it plunged you back down again.

This mix of the heart-stopping and the stomach-lurching (a true kinaesthetic experience) characterises some of the best sequences in Love Never Dies, Andrew Lloyd Webber's much-heralded follow-up to The Phantom of the Opera. This latter was – and is – the most commercially successful show in theatre history and, by virtue of that fact, is not an easy piece for which to write a sequel (the fans – or "phans" – are very possessive about the original) nor is it one which self-evidently demands a dramatic extension.

I did not bring up the St Giles' Fair idly. As anyone who has not been buried in the bowels of the Paris Opera for the past few months will know, in this new extravaganza – which could be nicknamed, with apologies to the postman, "The Phantom Always Wrongs Twice" – a decade is deemed to have passed and the eponymous disfigured, emotionally tortured composer is presented as having worked his way up from freak show exhibit to master-impresario of Coney Island, the pleasure-beach resort near New York.

And we see all this, at times, from the perspective of a child's corruptible wonder because (and here is where purists jib) it turns out that the Phantom and Christine, unbeknownst to the rest of us, did have carnal relations back at the Paris Opera. So when this now highly successful soprano and irreplaceable Muse of the Phantom fetches up for a singing engagement at Coney, with her hard-drinking, disaffected gambler of a husband, Raoul (excellent Joseph Millson), it is with the Phantom's own 10-year-old son in tow.

The original musical agonised over the possibility of unconditional love in a relationship of beauty-and-the-beast opposites and mutual professional inspiration. Add a child to the equation and (depending on your view of this young character's artistic provenance) it all becomes more tortuously complex or emotionally bogus.

What is in no doubt is the technical excellence of Jack O'Brien's seamlessly fluent, sumptuous (and sometimes subtle) production, or the splendour of the orchestra which pours forth Lloyd Webber's dark-hued, yearning melodies as if its life depended on them. Special praise should go to the lyrical lavishness of Bob Crowley and Jon Driscoll's designs, with their gilt interiors where the vegetation-imitating contours and giant peacock-plumage of Art Nouveau run rampant, and their ghostly external locations where a brilliantly deployed combination of flowing projection (timed to perfection with emotional/ rhythmic shifts in the music) and solidly presented stage-effects create a dizzying Coney Island of the mind.

The whole piece is presented as the spectral retrospective of the bitter Madame Giry (Liz Robertson), the woman who stuck by the Phantom, managed his amusement park and watched her daughter Meg (a vividly "vaudeville" and slowly curdling Summer Strallen) play second fiddle to Christine, before playing nemesis to the whole shebang. Therefore, in the stunning introductory sequence, which begins on the nocturnal boardwalk, the seafront buildings turn into a flapping rag of blatant stage-scenery. As the orchestra pumps out a macabre Coney Island Waltz of faintly nerve-racking nostalgia, shadowy carousel horses bound over the gauze scrim and foaming ocean breakers metamorphose into light-bulb-flashing ferris wheels. The Babylon shoreline looms at you like the ground seen from one of those contraptions.

As with the ice-glass carriage, manned by three glitteringly black-and-white mutants, to convey Christine and family to Coney, it's enough to turn a small boy's mind. And that is, in part, the point. My least favourite bit musically may be the stomping rock into which the score degenerates when the Phantom treats his son to the spectacle of his ingenious curiosities (a skeleton wheeling a writing desk; and, oops, concealed in the nick of time, the working life-size doll of his mother that the Phantom has harboured as a creepy faute de mieux). But I can see the psychological development intimated by Ben Elton and Lloyd Webber's book. Pathetically, the father wants the boy to move on from these so-called wonders to countenancing the Phantom's own (rather less inorganic) deformities. The world of ordinary fun persists achingly just outside. Some of the simplest and most moving moments come when there is a sudden switch from the interior murk of claustrophobic showbiz to a glimpse of searingly blue-skied Coney sunshine, so near and yet so far.

It's revealing that Andrew Lloyd Webber, who has cast leading roles in his most recent ventures by public vote on reality TV talent show, has not allowed the public anywhere near his casting decisions for Love Never Dies. This rather exposes how low-risk those TV experiments have been, geared as they have been to fairly safe properties such as The Sound of Music and Oliver!.

In a sense, Lloyd Webber has become hoist by his own petard. Having over-petted the public, he is now being badly mauled by a section of it – the Phantom fanatics who feel that they own the original more than he does. On both counts (casting and the right to do what he likes with his own material), Lloyd Webber has, for once, the moral high ground here. Ramin Karimloo may not be a physically imposing enough presence as the Phantom, but his marvellously supple voice can run the gamut from a seductive guttural whisper to the full blare of frustrated passion.

Looking gorgeous in a range of stylish period-outfits, Sierra Boggess's Christine boasts a voice that can pool and purl quietly and then knock you dead with her towering rendition of the climactic title number. She takes the song's emotion of stoical endurance in the face of unquenchable love and presents it first with a steady stateliness and then with heart-rending soar. The score may lack a duet as thematically and melodically interwoven as "The Music of the Night" from the original. But the leading couple sing beautifully together, like two fountains overtopping each other, in the lyrically staged balcony double duet of "Once Upon Another Time".

There's one issue on which on which I might side with the "phans". The ending (which I won't give away) feels phoney in the unconvincing completeness of its resolution. It makes what has preceded it abruptly feel a good deal less than the sum of its parts and cries out for more ambiguity. In short, it should be "phixed".

Phans' reaction: View from the stalls

Phantom devotees have given their assessments – some distinctly underwhelmed – of preview performances on blogs and web discussion boards. Here are some of the remarks.

*Just wish, apart from a very few highlights, that it wasn't so boring! Steve10086

*Audience in stalls gave a standing O, though the noise wasn't as tremendous as one might have expected. Applesarenice

*loved the show, brilliant cast, brilliant set. Monkeycarter89

*I hate to be so negative because the cast were great, Lloyd Webber is a genius and I love Jack O'Brien but it doesn't work mostly. Thundercat

*Very clinical and devoid of emotion. I didn't particularly care who lived or died. I just wanted to go catch the train home. Steve

*The critics will probably savage it but there is much to enjoy. Elixa

*May the show close as soon as possible in disgrace. LSD

*Dull. Like watching paint dry, and as we all know, paint never dries. West End Whingers

*It has a lot going for it – not least the excellent cast which, to be honest, should be a given, but I didn't find it faultless. Palatio

*Silly, shallow and superficial – Lloyd Webber trademarks these days. Horton

*Written by committee – and it shows. It's like a bad Hollywood film. The characters are thin or non-existent, the plot mind-numbingly predictable and the Phantom's magic has been lost. ECM