"The Cuckoo's Calling" is clearly meant as the first book in a series of detective novels. It introduces private detective Cormoran Strike and his secretary, Robin Ellacott, who soon finds herself engaging in work far beyond the usual call of secretarial duty. By the end of the novel, their first case is solved and the stage is set for the next one.
Is this as good a book, of its kind, as "Harry Potter"? Well, no. But still, all those who grew up on the Harry Potter series and, now being grown, would like a Rowling series for grown ups, have cause to rejoice in "The Cuckoo's Calling."
Warning: the Wikipedia article on "The Cuckoo's Calling" contains a plot summary -- in other words a spoiler. Whoever posted that article seems intent on destroying our enjoyment of the book. If you like mysteries, steer away from that article until after you have read the real thing. Check this out!