What does Geiger have to do with the story?

Geiger is a book dealer whose dealings turn out to be more sinister than they first appeared; he has a pornographic lending library that Marlowe describes this way: “Photos and letterpresses alike were of indescribable filth… elaborate smut” (26). Rather than indulging in such books as some might, Marlowe recognizes them as perverse and reprehensible. Marlowe stands in striking contrast to the man who left the volume behind: an lavish dandy with a cane and gold bordered wallet who, when he sees he has been trailed by Marlowe, hides behind a tree, departing the scene only after having safely ditched the book. Pornography such as this is not then for men of Marlowe's character, but for those who are wealthy, hedonistic, and without moral strictures.

Marlowe further reveals his disgust with sexual perversion when he visits Geiger's home that night, finding Carmen Sternwood naked and drugged, in the process of being photographed by Geiger, who has been freshly killed, shot three times. “The three shots had been somebody else's idea of how the proceedings might be given a new twist,” Marlowe thinks. “The idea of the lad [who killed Geiger]. I could see merit in his point of view”(31).