Bob Arctor, a substance-D drug user in mid-90's California 
 (view spoiler)[ 
 Bob / Fred is actually a deep undercover narcotics officer, whose identity is hidden from superiors and colleagues through use of a 'scramble suit' 
 Substance-D, death, drug of unknown source, kills its users, erodes the connections between the hemispheres of their brains 
 Eventually Fred is tasked with surveilling himself (Bob), while he suffers the effects of the drug, another consciousness may be emerging in his head, and he is losing track of who he is 
 telling scene as he reviews holographical surveillance tapes of himself, commentating on himself as third person 
 eventually succumbs to near vegetative state and is sent to New-Path treatment facility (ultimately the source of the drug...) 
 (hide spoiler)] 
 in part inspired by author's own experiences, Philip is Bob is Fred is Bruce 
 fascinating view of the obsessions, segues, paranoias of drug users and the trajectory of their lives