In Colin Brush's debut novel, Exo, Earth's oceans have been overtaken by an encroaching gray substance that attracts humans with its siren call and disintegrates anyone who touches it. Among the few humans on the shore resisting its lure is Mae Jameson, who lost her husband to it decades ago. When she discovers that a scientist living nearby has been murdered, she's compelled to find out who killed him and takes responsibility for the young child he left behind.
This atmospheric novel takes place in a thoroughly imagined setting in which Earth is largely deserted and humanity is scattered across the solar system in orbital habitats and dome-shielded cities. The plot is a mathematical adventure featuring a scientist's journal and a hyperdimensional entity that will delight fans of hard sci-fi. A vividly constructed cast of characters reckons with Earth's demise: a cult priest worships the encroaching ocean; a perpetually helpful mechanic fixes everyone's jerry-rigged machines while desperately trying to find a way off the quarantined Earth; a pair of aging sisters hosts anyone who wants to visit the garden they tend around their homestead.
As Mae investigates the murder, the novel ramps up into a riveting mystery, although it is one that culminates in a scene likely to shock and unsettle readers especially sensitive to matters of fertility. But to say more would also spoil one of the central reveals of the book. Exo builds on cherished staples of postapocalyptic fiction: a ragtag collection of characters who help one another out in an inhospitable landscape. But the murder adds another layer, casting them all in the light of suspicion. --Carol Caley, writer