Neither traditional thriller nor standard police procedural, “Sheerwater,” the debut from Leah Swann, piles drama upon drama with calibrated evocation. The book kicks off powerfully: driving to a new life on Victoria’s Great Ocean Road, escaping her fraught relationship with a volatile husband, a mother leaves her two young boys momentarily in the car while helping save the passengers of a crashed light plane, and when she returns to the car … the boys are gone. From there the book spirals in intensity, enmeshing the husband and a troubled local doctor. Each time a formulaic plot twist seems certain, author Swann subverts the genre and takes the story askew. The writing is as ferocious as the plot, bringing the coastline and the characters’ inner lives successively into the spotlight. If I caviled at some plotting confusion between the novel’s aims, I suspect that reflects more upon my faith in existing genre tropes than upon anything else, and the pages of “Sheerwater” turned in a blur of fascination. A fine read.