What is the theme in The Crying of Lot 49 by Thomas Pynchon?

In The Crying of Lot 49, Pynchon combines the themes of decay and conspiracy developed in V. with observations on communication theory. The main character, Oedipa Maas, has been given the job of administering the estate of her deceased lover, Pierce Inverarity, who in addition to being a real estate tycoon, was also a stamp collector. In the course of investigating Inverarity's holdings, Oedipa uncovers a conspiracy in opposition to the postal system which dates back to the sixteenth century.