Overall, the development of theme between the book and the film adaptation are comparable. Both thematically present the protagonist's addict psyche as representative of an element, though a dark element, of universal human psyche (as opposed to the deranged psyche of one unfortunate man). Both display the interlinkage between the cosmos of the mind and the cosmos of external forces that exert unwanted control over the psyche. In other words, in both the book and film, the protagonist does not willingly follow his dark path but forces controlling him decide the route of his path. In this sense, fate is a theme in both.
One decided difference in theme presentation between the book and the film is that the film represents in some regards a composite of a number of Burroughs' works while it also includes more real-life events and relationships than the book incorporates. The film is also more self-reflexive than the book. It provides more glimpses of the creative process, provides more references to metafiction while more processes of creation unfold within the filmatic creation than are possible within the book. The thematic reference here, one that is heightened in the film over the book, is how the creative process is interlinked with the psyche, particularly with the dark psyche of universal humanity.