Throughout the book, Pynchon introduces many themes and criticisms that are not only very relevant to today but also modern and applicable. Here are some of the most important themes.

Communication
Communication is an important theme in this book and it is shown mainly through the great chaos that is going on throughout the book. Throughout the book there are plots and sub plots within pages. Everything in the story is told chaotically. In the end it is the chaos and lack of communication that causes many problems. This book was written at a time when many technologies were changing the way we communicated and how it was done. Pynchon tries to use this to show the theme that communication is one of the most important elements of society that can not be replaced or changed.
examples in text:

And the voices before and after the dead man's that had phoned at random during the darkest slowest hours, searching ceaseless among the dial's ten million possibilities for that magical Other who would reveal herself out of the roar of relays monotone litanies of insult, filth, fantasy love, whose brute repetition must someday call into being the trigger of the unnamable act, the recognition, the Word.(Pynchon 86)

Important vs. Unimportant
Throughout the book Oedipa is chasing something that she is not even sure exists. She experiences many things that either prove to her that it exists, while some lead her otherwise. Either way she is not sure what to think and often many of her experiences turn sort of unreal and imaginary. This adds exclamation the point of the important vs the unimportant because Pynchon raises the point that Oedipa may be spending all of her time chasing something that is unreal and in the long run unimportant. It also poses the question of what in life is really worth finding out
and what should you just let go.

Behind the hieroglyphic streets there would either be a transcendent meaning, or only the earth. In the songs Miles, Dean, Serge and Leonard sang was either some fraction of the truth's numinous beauty (as Mucho now believed) or only a power spectrum.(Pynchon 58)