At its core, "Long Bright River" is a story about the enduring, albeit complicated, bond between sisters. Despite their vastly different lives and the challenges they face, Mickey and Kacey share a deep connection rooted in their shared history. Their love for each other, though tested by addiction, loss, and violence, ultimately drives the narrative and showcases the profound strength and resilience of familial love.

Moore doesn’t shy away from depicting the harsh realities of the opioid epidemic gripping America. The story offers a raw and unflinching look at the devastating impact of addiction, not just on individuals but on families and communities as a whole. Through Mickey's work as a police officer and Kacey's struggles, we see the human cost of this epidemic, forcing readers to confront the complexities and consequences of this pervasive issue.

Both Mickey and Kacey are haunted by past traumas and seeking redemption in their own ways. Mickey, grappling with guilt and a sense of responsibility for her sister's fate, seeks solace in her work while battling her own demons. Kacey, lost in the throes of addiction, yearns for a way out of the darkness that consumes her. Their parallel journeys of self-discovery and the possibility of finding redemption amidst tragedy form a powerful emotional core of the novel.