In J. K. Rowling’s latest novel, “The Silkworm,” her appealing detective hero Cormoran Strike is back, and so is his resourceful sidekick, Robin Ellacott, a gumshoe team that’s on its way to becoming as celebrated for its mystery-solving skills as Nick and Nora Charles of “Thin Man” fame, and Mikael Blomkvist and Lisbeth Salander (a.k.a. the girl with the dragon tattoo).Ms. Rowling, writing under the pseudonym Robert Galbraith, introduced the pair a year ago in “The Cuckoo’s Calling,” a novel that plunged the rumpled, Columbo-esque Strike into the posh world of supermodels, rock stars and movie producers. (The woman at the center of that case came across as a kind of cartoon version of Kate Moss with a rocker boyfriend who bore more than a passing resemblance to Ms. Moss’s onetime beau Pete Doherty.)In the “Silkworm,” Ms. Rowling concocts a case — involving the mysterious disappearance and grisly murder of a self-important novelist named Owen Quine — that plops these unconventional sleuths into the even more rarefied world of literary London, sending up the swollen egos and clashing ambitions of writers, editors and publishers vying for fame and top-dog standing.