The Cassie Dewell series is a collection of crime novels written by author C.J. Box. The series follows the character Cassie Dewell, a private investigator in the American West, as she tackles complex cases involving missing persons and criminal activities. The stories are known for their suspenseful plots and rich descriptions of the landscape. Set primarily in Montana, the series explores themes of justice, morality, and the challenges faced by women in law enforcement. Each book builds on Cassie's character development and her relationships with other characters, making it a compelling read for fans of the crime fiction genre.