From what I understand it (and no, I haven't read the book), it is largely dominated by minimalism and rich I/O such as pipes and sockets. (all of which, you will notice, from a programmer's point of view, have file descriptors, and are read and written through the same calls; again, back to "everything is a file")

mcc suggested I append a hardlink to "jwz: The Rise of ``Worse is Better''". Very well, but I don't think much of those who bitch about UNIX sucking. Either way, an interesting essay about the UNIX philosophy.