Stuart MacBride begins his latest crime novel, a stand-alone featuring anti-hero DC Ash Henderson, in typically grisly style: 12 girls go missing over a period of 12 years, always three or four days before their 13th birthdays.

A year after their initial disappearance, their parents are sent a gruesome "birthday" photo of them terrified and tortured, the first of many sent every anniversary.

It's about as horrible as you could imagine. And then it starts to career madly into the realms of the ludicrous, defying all logic to reach a car-crash of several denouements that have the constantly beaten-up Henderson (anyone else would have been hospitalised for months) chasing murderers after shooting himself in the foot.

MacBride is famous for his black humour and gritty realism, so he's having plenty of fun here. The balance between realism and the grotesque may begin in favour of the former, when we see a victim of the "Birthday Boy" torturer, then Ash Henderson himself, who's hiding a secret. His eldest daughter, Rebecca, was kidnapped just before her 13th birthday, too, and every anniversary he has also received a photo detailing a different stage of torture. The abduction has broken up his marriage and left him a damaged man, in hock to some serious gangsters. However, he keeps Rebecca's abduction to himself so that he can stay on the Birthday Boy case.

When another girl disappears and the first body turns up, the race begins to find the killer before he kills again. In this race, he's assisted by criminal psychologist Alice McDonald.

So far, so grim, guaranteed to keep you reading and give you nightmares – and then it all goes a bit bonkers. Actually, pretty much everyone in this book is bonkers. Alice herself is more than a little eccentric; the gangster's assistant chasing Henderson for money is a crazy Irish woman, Mrs Kerrigan; a radio DJ, Sensational Steve, refers to himself in the third person; a former DI, Henry Forrester, is almost insane with alcohol abuse; and a lunatic "rat-catcher" in the morgue holds dead rats like babies.

Henderson is pretty mad, too, beating up anyone in reach after his youngest daughter, Katie, also disappears a few days before her 13th birthday (Henderson might have seen this one coming). Perhaps it is the water: Henderson's beat is Oldcastle, an area possibly poisoned by too much mercury from chlorine gas factories during the war, giving it the highest number of mental health cases anywhere in the country.

It's comforting that a novel so full of bonkers folk is also crammed with women. They're there assisting Henderson, like Dr McDonald, they're the girl victims, the perpetrators of violence like Mrs Kerrigan and Terri Whitaker, wife of another gangster, or involved with Henderson like stripper Susanne. Maybe women love MacBride's work and he's reflecting their loyalty. Certainly there's very little psychologically to make women feel scared – the girl victims could easily be 13-year-old boys, so hazily are their interests and cares sketched out – which is surprising, given that one of the main characters is a psychologist.

Indeed, the revelation of the Birthday Boy's identity and the psychological explanation of the crimes only rates about a page. Psychology doesn't interest MacBride very much.

So what does interest him? Speed, certainly – this zips through a week in Henderson's hilariously implausible life like an episode of 24. And noise – this is one of the noisiest books I've ever read, full of radio interference, people talking over each other and shouting each other down or slamming their fists into one another, cracking bones and smashing heads. Ultimately though, it's not the identity of the killer that interests MacBride, or the reasons why people kill. It's as if his real fascination is in having fun with his readers. As though he's saying to them, come on, you're not really buying any of this, are you? His royalty statements will tell him, of course, that they are.

Birthdays For The Dead

Stuart MacBride

HarperCollins, £14.99