The Ink Black Heart by Robert Galbraith (Sphere, £25) At 1,024 pages, the sixth outing for private investigators Cormoran Strike and Robin Ellacott is the longest yet, but although there are longueurs, this tale of internet pile-ons repays the commitment. Edie Ledwell, co-creator of popular YouTube cartoon The Ink Black Heart, approaches the agency hoping to discover the identity of her online persecutor, Anomie, but is turned away because of an already heavy workload. Shortly afterwards, Edie is found murdered in Highgate Cemetery in north London, with her collaborator and former boyfriend lying seriously wounded nearby. He is unable to name the assailant, but Anomie, who has invented a game based on the cartoon, claims to be responsible. Strike and Ellacott attempt to unmask Anomie, entering the game and interacting with The Ink Black Heart’s obsessive fans. This novel could certainly be seen as Galbraith AKA JK Rowling’s riposte to the treatment meted out to her online, but I suspect it’s not a coincidence that it’s set in 2015, the time of the #Gamergate campaign of misogynistic harassment which, as here, included doxing, rape and death threats, as well as conspiracy theories. This is a cautionary tale of the virtual world’s impact on real people’s lives. The Skeleton Key by Erin Kelly (Hodder & Stoughton, £16.99) A different type of fandom is examined in Erin Kelly’s latest: armchair treasure hunters, such as those obsessed over Kit Williams’s 1979 puzzle story book Masquerade. Here, the inspiration is the similarly successful The Golden Bones, created by artist Frank Churcher: the tale of murdered Elinore, whose bones, made from gold and precious stones, are buried in sites across England. Now only one remains undiscovered. Churcher has grown in wealth and stature, while his family, who enjoy a bourgeois boho existence in Hampstead in London, have become increasingly dysfunctional – and some of the treasure hunters haven’t fared too well, either. The clan meet to celebrate the 50th anniversary of the book’s publication, and a film crew is on hand to make a documentary – but when the “big reveal” of the final bone goes disastrously wrong, metaphorical skeletons begin cascading out of cupboards. With rich characterisation and intricate yet propulsive plotting, Kelly is at her considerable best as she mercilessly fillets monstrous egos and toxic relationships while ramping up the tension. The Bullet That Missed by Richard Osman (Viking, £20) The third book in the bestselling Thursday Murder Club series sees the denizens of the upmarket Kentish retirement village embark on another investigation. This time, former spy Elizabeth, retired nurse Joyce, psychiatrist Ibrahim and former trade unionist Ron are looking into the disappearance of Bethany Waites, 10 years earlier. Waites, a journalist who had been investigating a massive VAT fraud, was presumed to have died when her car plunged off a cliff at Dover. The body was never found but the circumstances were suspicious, and as the pensioners begin to investigate the cold case becomes red hot. Kidnapping, blackmail and murder ensue, but the quartet take it all in their stride, just as they do the vagaries of ageing. Warm, witty and – despite the body count – soothing as ever, this is peaceful reading for an autumn afternoon. Sometimes People Die by Simon Stephenson (Borough, £14.99) Returning to practice in 1999 after being suspended for stealing opioids, a young Scottish doctor takes a job at the only place that’ll have him: St Luke’s, an understaffed, underfunded NHS hospital in London’s East End, which looks “like an asylum that a distracted child had amended with half a dozen unmatched Lego sets”. As he struggles to fight a bewildering array of diseases he’s only read about in textbooks – dengue fever, scurvy, rare genetic syndromes – often consulting via an interpreter, a growing number of unexpected patient deaths create an atmosphere of paranoia. The police bumble about ineffectually; one staff member after another becomes the prime suspect; a colleague takes their own life, and our unnamed narrator has a relapse … Written with an Adam Kay-style sardonic wit and interspersed with descriptions of the real-life careers of murderous medics, it’s certainly engrossing, although crime aficionados might wish for a more focused, less picaresque plot. Marple: Twelve New Stories by various authors (HarperCollins, £20) Although crime writer Sophie Hannah has written novels featuring Hercule Poirot, this is the first time the Agatha Christie estate have allowed a reintroduction of Miss Marple, reimagined here in a hugely enjoyable collection of 12 new stories by female writers ranging from Naomi Alderman and Jean Kwok to Dreda Say Mitchell and Leigh Bardugo. The spinster sleuth who, in Christie’s own words, “expected the worst of everyone and everything, and was, with almost frightening accuracy, usually proved right”, can be found solving crimes in Manhattan (Alyssa Cole), the Amalfi coast (Elly Griffiths) and Cape Cod (Karen M McManus), as well as on her home turf of St Mary Mead (Val McDermid and Ruth Ware) or the equally outwardly respectable Meon Maltravers (Lucy Foley). Some offerings may be more in the golden age tradition than others, but there’s enough beady, tweedy Marple ingenuity here to satisfy the most fastidious Christie fan.