Communicating Sequential Processes

My recent interest in Erlang has motivated me to reread C.A.R. Hoare's classic Communicating Sequential Processes . If you are interested in software development and concurrency then I implore you to read (and re-read) this important work. If you won't take my word for it then consider the words of Edsger W. Dijkstra.

The most profound reason [the manuscript was eagerly awaited] , however, was keenly felt by those who had seen earlier drafts of his manuscript, which shed with surprising clarity new light on what computing science could—or even should—be. To say or feel that the computing scientist’s main challenge is not to get confused by
the complexities of his own making is one thing; it is quite a different
matter to discover and show how a strict adherence to the tangible and quite
explicit elegance of a few mathematical laws can achieve this lofty goal. It
is here that we, the grateful readers, reap to my taste the greatest benefits
from the scientific wisdom, the notational intrepidity, and the manipulative
agility of Charles Antony Richard Hoare.