What are the motifs in City of Glass by Paul Auster?

Obsession and loss of self is also a prevailing motif of the novel. In each case, the main character becomes obsessed with the case and loses his perspective to the point where they are cut off from most human contact and can't help themselves. Quinn lives in a garbage dumpster for several months, so obsessed is he with the Stillmans. When he runs out of money, he has no place to go but the Stillman's apartment where the experiment with darkness takes place. By that time he is helpless.