The actor and comedian Ardal O’Hanlon’s first novel, 1998’s The Talk of the Town, hinted at the emergence of a distinctive literary talent, equal parts Flann O’Brien and Irvine Welsh. His follow-up has taken nearly a quarter of a century to appear, and unfortunately the boldness of his original debut has been replaced by a jarring mixture of whimsy and brutality. No doubt O’Hanlon’s publisher would like it to be compared to Paul Murray and Colin Bateman, but Brouhaha would probably never have been published were it not for O’Hanlon’s status.

The book is set in Tullyanna (“a smallish border town populated by just three thousand pinched faces and all of them secretive’), a poverty-riddled hellhole that is home to the usual cliches: a reluctantly retired detective trying to do the right thing, a frustrated journalist and the usual supporting cast of hardmen turned politicians, the lucky few who escaped small-town ennui and the far greater number who never had a chance. (There are, of course, Springsteen references to hammer this point home; this is not a subtle book.) All are brought together by the apparent suicide of the street artist “Dove” Connolly, whose death seems to be linked to the disappearance of Sandra Mohan, last seen a decade earlier.

The novel’s greatest flaw is that O’Hanlon seems unsure of the story he wants to tell. He isn’t an untalented writer and can come up with a neat phrase and amusing dialogue – I enjoyed the detective’s heartfelt complaint “What normal person could function without a decent set of delusions?” – but Brouhaha careers between state-of-the-nation metaphor, black comic thriller and half-baked mystery, without ever settling on a coherent tone. If O’Hanlon writes another novel, he would be well advised to return to the mood of The Talk of the Town and to treat this disappointing book as an aberration.

• Brouhaha by Ardal O’Hanlon is published by HarperCollins (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply