Have you read it yet? That was the question on everyone's lips for a year during lockdown, as we caught up with the slightly incredible fact that the geeky bloke from BBC1's quiz Pointless had completely reinvented the detective novel.

Richard Osman's dazzling comedy thriller The Thursday Murder Club, with its quartet of septuagenarian sleuths in an old folks' home, proved the publishing industry's biggest seller since Harry Potter.

But five years on, everybody's asking another question, and in a very different tone of voice – baffled, disappointed, shocked: Have you seen it yet?

The film adaptation, directed by Chris Columbus – the man behind the smash hit Home Alone – and co-produced by Steven Spielberg, ran for just a week on cinema release before transferring to Netflix. It features a cast of triple-A list actors, any one of them big enough to carry a movie on their own.

And it is awful. Not so-bad-it's-fab sort of awful. Just a bland, dull, dreary travesty, wasting all the talent involved and guaranteed to leave any viewer who hasn't read the book wondering what all the fuss was about.

Like so many fans, when I devoured the novel I found myself almost looking forward to retirement so my wife and I could spend our days with new chums in a welcoming community, enjoying a fresh lease of life with intriguing adventures and lots of strawberry sponge.

Throughout the two hours of the film, I also kept thinking wistfully of retirement... immediately, so I wouldn't have to watch this dross to the end.

Osman's idea, which he wrote up in his spare time over the course of 18 months, is so ingeniously simple, it's remarkable that no other crime novelist came up with it before him.

At a sheltered complex for well-to-do OAPs, four elderly friends with a taste for true crime meet every Thursday in the jigsaw room, to eat cake and discuss unsolved cold cases.

When the home is threatened with demolition, they set about organising a protest. But after the unsavoury men behind the proposed sell-off meet sticky ends, the Thursday Murder Club finds itself with a real mystery to unpick.

At this point, I should say that not everyone hated the film. The Times' film critic gave it four stars and it has a 76 per cent score on the movie review website Rotten Tomatoes.

But my own reaction was: How could the adaptation be so dire? Part of the problem is the casting. Remember Pierce Brosnan in Mamma Mia, murdering Abba songs like a tone-deaf serial killer? 

That was a career highlight compared to his turn as Ron Ritchie, the tactless ex-trade union boss who provides the muscle for his fellow sleuths.

Brosnan, whose impossibly suave good looks made him a natural James Bond, is still at 72 a ridiculously handsome man. But he isn't burly, tough, combative or chippy – all the qualities that sum up Red Ron.

In one scene, where the ageing radical leads his army of pensioners in a march against the property developers, Brosnan makes him look like a gentleman farmer at a bad-tempered village fete.

In fairness to him, he admits he was wrong for the role. When his agent sent him the script, his first thought was that Hollywood had him confused with Ray Winstone.

But that doesn't excuse his attempt at a ruffty-tuffty Cockney accent, which keeps lapsing into Irish. Clearly, the effort was too much, since in half his scenes he just does standard English.

Equally bad is Celia Imrie as Joyce Meadowcroft, the newest member of the club. She is Osman's cleverest creation, a truly original character who is also instantly recognisable. If you've never read the first page of the book, it's a treat – Joyce's voice is so familiar, you'll feel as if you've known her all your life.

She's fluffy, self-deprecating, kindly, incorrigibly nosey and thoroughly in awe of people she regards as more important than herself. 

But she also knows her own worth, and will stubbornly stand her ground when people (especially her own daughter) try to push her around. Joyce is the lynchpin of the book. In the film, she's an irrelevance. You could cut all her scenes and her absence wouldn't even be noticed.

Imrie fails to convey any of her scatty charm or sentimentality. Instead, Joyce becomes a shrewish busy-body with a foul mouth and a ghoulish interest in photographs of murder scenes.

Her chief purpose is to feed everyone cake and prompts. When anything needs explaining – and half the dialogue consists of explanations – it's Joyce who sits there nodding. 

She could have been the one to guide us through the story, pointing out the clues and reminding us who's who, if Columbus had thought to make her the narrator. A Joyce voiceover may have supplied the friendliness and wit it wholly lacks.

Instead, the director focuses on Helen Mirren, often to the exclusion of everyone else. She plays ex-spy chief Elizabeth, who makes no secret of being a former secret agent – she drives an Aston Martin, which she boasts was a gift from her colleagues at MI6.

In the second hour, if you make it that far, each of Mirren's scenes is followed by... another scene all about Mirren. She's confronting the hapless police inspector (Daniel Mays), then she's waking up in the middle of the night to tackle an intruder, then she's updating her fellow sleuths on what she's discovered, then she's grilling a murder suspect in a coma.

It feels as though the film was originally 45 minutes longer, before being savagely pruned... perhaps because early screenings showed some audiences were actually dying from boredom before the denouement.

At one point, Elizabeth has to explain to Joyce what Ron and his pal Ibrahim (Ben Kingsley as the fourth member of the club) have been doing off-screen – presumably to save time. What's the point of hiring an actor as subtle and versatile as Kingsley, if you're going to leave him with nothing but the odd line here and there?

Much of the screenplay, by comedian Katy Brand and playwright Suzanne Heathcote, is so leaden that Kingsley is probably grateful to have been spared.

We're told repeatedly (as every plot point is hammered down like a coffin nail) that Ron's son Jason (Tom Ellis) is a three-times world middleweight boxing champ. Yet Ron tells him: 'You were a contender, son.' How can a triple world champion be just a contender?

One exchange follows a row between the villainous property moguls – also people smugglers of Polish builders – Tony Curran and Ian Ventham (Geoff Bell and David Tennant). This argument is watched by the four Murder Clubbers, gathered like children at a Punch and Judy booth. As Ventham stalks off, Elizabeth calls out: 'Tony, what's going on?'

'What's going on, Liz?' he retorts. 'Ventham! That's what's going on.' And so on, ad nauseam.

Richard E Grant has a cameo, as another villain, who runs a florist's on the side. When Elizabeth beards him in his lair, he is snipping the stems off roses with outsize secateurs so ferociously the thorns are slashing his skin. He literally has blood on his hands.

Is that meant to be funny? Surreal? Whatever the intention, it fails, and leaves Grant looking like a guest star in a sketch show.

Brosnan has a line that sums up the whole sorry business. Riffling through a folder full of clues, he announces in that bizarre mixture of Blarney stone Irish and Kray Twins gangster: 'I think it stinks... Stinks. Stinks like a rat up a drainpipe.' Doesn't it just.