I wasn't particularly interested in JK Rowling's first post-Potter novel, The Casual Vacancy—I still haven't gotten around to reading it, despite being a giant Harry Potter fan. But when news broke that JK Rowling had written a detective novel, The Cuckoo's Calling, under a pen name, I bought the ebook immediately. I feel the tiniest bit guilty about this—like it outs me as an unadventurous sort of reader, willing to support an author so long as they continue to do just what I want them to do. And in Rowling's case, I want fun genre fiction, not so much dry-sounding literary fiction about tiny British towns.

The Cuckoo's Calling is a very good, character-driven detective novel, more "little grey cells" than CSI: London. Rowling's detective, Strike, is a battered, one-and-a half-legged veteran of the war in Afghanistan, a former military man who retired after his leg was blown off to open a detective agency. Hounded by creditors and short on clients, a temp agency mistakenly sends him a secretary he can't afford on the same day that he's visited by a client who wants him to prove that a high-profile suicide, in which a model was presumed to have jumped to her death, was actually a murder. Accompanied by his plucky new secretary, Robin, Strike takes on the case, which involves high fashion, drug-addict street kids, beautiful women with mysterious pasts, and plenty more.

The most surprising thing about The Cuckoo's Calling isn't the tightly organized plot (the Harry Potter books were full of mysteries) or the compelling character dynamics (ditto), but rather Rowling's sense of humor, which is adult and sly and intelligently deployed. Take, for example, a joke about a red-breasted robin that is not only funny on its own, but deftly reinforces the initial awkwardness between Strike and Robin, two attractive straight people working in close proximity. (Robin is engaged, and there's not much "will-they-or-won't-they" in their relationship. I hope it stays that way in any future sequels.) Strike has the "high, bulging forgehead, broad nose and thick brows of a young Beethoven who had taken to boxing"; "his thick curly hair, springy as carpet, had ensured that his many youthful nicknames had included 'Pubehead.'" Pubehead! JK Rowling said "pubehead"! (This is perhaps just the kind of commentary Rowling was trying to avoid by writing under a pseudonym.)

While most of the book focuses on Strike, a classically cranky-yet-brilliant private investigator, a few chapters are dedicated to Robin, the temp who's always secretly dreamed of being a detective. Robin's a great character, and Rowling is interestingly sensitive to the plight of a pretty girl for whom male attention, welcome and unwelcome, is constant: "Robin was laughing in the slightly grudging manner of a woman who is entertained, but who wishes, nevertheless, to make it clear that the goal is well defended."

The Cuckoo's Calling proves what Harry Potter fans have argued all along: That Rowling's a great, fun writer whose novels shouldn't be dismissed simply because of the genre she's writing in. Powell's currently has the title on backorder, if you're patient, or Amazon's got it in a few formats.