The Crying of Lot 49

The book is about a fictional conflict between the two first mail distribution companies to exist, Thurn und Taxis (which actually existed and was the first firm to distribute postal mail) and Tristero, which is a fictional invention of Pynchon's.

After being defeated by Thurn und Taxis in the 1700s, the Tristero organization goes underground and continues to exist, with its mailboxes in the least suspected places. In the plot of the novel, the existence and plans of the shadowy organization are revealed bit by bit...

... or, then again, it is possible that the Tristero does not exist at all. The novel's main character, Oedipa Maas, is buffeted back and forth between believing and not believing in them, without ever finding firm proof either way. The Tristero may be a conspiracy, it may be a practical joke, or it may simply be that Oedipa is hallucinating all the arcane references to the underground network, that she seems to be discovering on bus windows, toilet walls, etcetera.

As in his earlier novel, V, Pynchon seems to be making a point about human beings' need for certainty, and their need to invent conspiracy theories to fill the vacuum in places where there is no certainty.

In addition to the above-mentioned postmodernist interpretation, there is also the theory that Pynchon was influenced by the racial tensions in southern California that would later turn into riots across the country. See Pynchon's article A Journey into the Mind of Watts, about the 1965 Watts riots. [1]