What is the theme in Dog Soldiers a Novel by Robert Stone?

Heroin is one of the main themes in the story. It becomes so important that it takes over the minds of those dealing with it. Stone has a clear picture of the drug culture and how it changes people, particularly during trying times. Early in the story Charmian shows Converse a brick of heroin and he examines it. Converse tries it and becomes ill because of the high quality and strong effect it has on him.