A Simple Favour is the most cleverly marketed film of the year. Watch a trailer or two and you’ll walk in expecting a thorny thriller in the vein of Gone Girl or The Girl on the Train. The kind of film that boasts unbelievable twists and unlikeable characters. And a tonne of style, too; just feast your eyes on this gorgeous poster, rendered in pastel colours and promising a fashion-forward aesthetic with more than hint of old-fashioned glamour. A Simple Favour might be directed by Paul Feig – responsible for Freaks and Geeks, Bridesmaids and, more recently, Ghostbusters – but the trailers tiptoe around this, promising a “darker side”.

The promise of the marketing doesn’t go unrealised. A Simple Favour is stylish, filled with twists, and certainly more than a few shades darker, tone-wise, than something like Bridesmaids. However, this marketing ingeniously obscures the true nature of A Simple Favour as a self-aware, genuinely funny spin on the overheated airport novel genre. This is an honest-to-goodness comedy; maybe not in the same way that Bridesmaids was a comedy, but undeniably full of laughs … with a razor-sharp edge.

I haven’t read Darcey Bell’s novel upon which the film is based, but if the reviews are anything to go by – and, hoo boy, don’t book reviewers like to spoil every last detail of a story! – it’s a pretty stock-standard, unapologetically ludicrous thriller. There are a few ways to adapt a story like this. First up, you’ve got the deadly serious take, à la Tate Taylor’s suffocatingly unappealing The Girl on the Train. Or you can follow David Fincher’s lead, cloaking your subject material in a veil of seriousness that gradually slips away to reveal an acerbic black comedy. Feig strikes a different path altogether, dialling up the camp – with the aid of able assistants Blake Lively and Anna Kendrick – and poking so much fun at its own silliness that it approaches self-parody …in a good way.

The story of A Simple Favour begins, as per its title, simply before becoming incredibly convoluted. The first half hour or so centres on the friendship between mousey single mum Stephanie Smothers (Kendrick) and PR executive Emily Nelson (Blake Lively), as sharp-tongued as she is sharply-dressed. They bond over martinis and secrets before Emily mysteriously disappears, and things shift into thriller mode. Stephanie goes full Nancy Drew, investigating Emily’s obscured past, her husband (Crazy Rich Asians’ Henry Golding), her employer (a flamboyant Rupert Friend) and sharing her findings on her mommy vlog.

The plot, adapted faithfully from Bell’s book, is at once beside the point and the entire point. The second act isn’t as purely funny as the first – though there are still plenty of laughs – but it is legitimately gripping, and even spooky, as you try and figure out what happened to Emily. As is often the case with these tales, the actual ‘what happened’ is the least interesting part; A Simple Favour’s only weak point is the ten or so minutes it spends unspooling the convoluted machinations that led to Emily’s disappearance. But thankfully, a no-holds-barred finale, favouring recalling Community’s “Conspiracy Theories and Interior Design” episode, acknowledges and celebrates the ridiculousness of Bell’s overheated plotting.

The pleasures of A Simple Favour extend beyond mysteries and jokes, however. Feig – who’s never struck me as an especially visual director in the past – has outdone himself here by adopting a classical, delightfully colourful aesthetic. The clothes, in particular, are fabulous; it’s rare to see a Hollywood film nowadays so unabashedly celebrate fashion outside of a period piece, while the cinematography and colour scheme consistently complement the costumes.

The real highlight, though, is Anna Kendrick. Don’t get me wrong, Lively is great too – spitting one-liners like it ain’t no thing – but Kendrick is asked to make an entirely implausible character not only realistic, but warm and likeable and funny. She succeeds with flying colours; much like Dakota Johnson in Fifty Shades of Grey, there’s a twinkle in her eye that tells you how much fun she’s having with the material. With a lesser actress in the lead, the film would’ve fallen apart, but Kendrick makes it sing. (No, not literally; this isn’t another Pitch Perfect.) Honestly, it’s the kind of performance that warrants Oscar attention it almost certainly won’t receive.

A Simple Favour is that rare beast of a film that manages to take a familiar genre and make it feel fresh. It’s a gripping thriller, a stylish drama and a hilarious comedy; do yourself a favour and go see it.