If you liked Curtis Road's "Microsound", you might like this book. However, be warned that it is not for the faint of heart. You need to be well versed in music theory and mathematics to get the most from it. It has a very academic tone, but has some unique things to say about algorithmic composition that makes it worthwhile. Also be warned that much of it is translated from the original French, so that makes some phrases in the book seem oddly worded. I guess I would best describe it as the "Godel,Escher,Bach" of algorithmic composers. It's rough going, but once you "get" what Xenakis is saying, you will have a perspective on algorithmic composition that is invaluable.
This book includes:
1) six chapters that are the translation of Musiques formelles, including the appendixes.
2) two chapters that are translations, with some additions, of the chapters "Vers une metamusique" and "Vers une philosophie de la musique" from "Musique Architecture".
3) "New Proposals in Microsound Structure", where Xenakis challenges sound synthesis by Fourier analysis and proposes a new synthesis based on probability theories.
4) "Concerning Time, Space and Music", which is similar to the article "Sur le temps" (1988). This paper describes time as intrinsically related to space and then ties this relationship to music.
5) "Sieves" and "Sieves : a User's guide," which constitute the two sections of the article "Sieves" (1990). The first chapter explains in detail the construction of sieves and the second reproduces the computer program that generates this construction. Sieves are integer sequence generators that can help generate pitch scales and rhythm sequences in compositions.
6) "Dynamic Stochastic Synthesis", which involves multiple levels of probabilistic functions that determine the break points in an envelope that in turn describe one cycle in an audio waveform.
7) "More Thorough Stochastic Music" provides the program of dynamic stochastic analysis that was used for the first version of Gendy, which was a computer program written by Xenakis that performed sound synthesis.
8) an annex on "The new UPIC system" based on an article from 1990 written by the engineers at CEMAMU at the time (G. Marino, J.M. Raczinski, M.H. Serra). CEMAMU is an acronym for "Centre d'Etudes de Mathematique et Automatique Musicales". The UPIC console is a direct-input graphics device that allows for one to escape the messy complexities of musical notation in the scoring of complex electronic sounds.
It is hard to find anything on the web written by Xenakis that is not in French, so this book is about the only way for English speakers to enjoy this man's work.