Don't be so impressed. I was able to find an unpublished translation online by John Dack and Christine North. It would be very easy for me to turn this review in a long essay most of which would be a polemic decrying the lack of English translations of Schaeffer's writing (actually, with the exception of a few short essays and excerpts, none of Schaeffer's books have been translated). With the current resurgence of interest in phenomenology AND semiotics, it would be crucial to have access to his writings on music, media theory, and communications all of which were heavily influenced by both. As for Chion's GUIDE, there is a funny story about Schaeffer complaining that what took him over six hundred pages to explain only took Chion under 200. The GUIDE is probably the best review we have of Schaeffer's ideas and really demonstrates that most English-language researchers and practitioners of musique concrete have no accurate understanding of Schaeffer's ideas. After I finished the Dack/North translation, I went back to all the music/sound art books in my library that treat Schaeffer's ideas. Without exception, every Anglophone writer gets it wrong. As for the organization of the GUIDE, Chion takes Schaeffer's book and rearranges its ideas into an accumulation of terms where each builds on the preceding going from general concepts to the most detailed terminology describing the five phases of analyzing the sound object. It's incredibly useful. And yet while I feel like the book completely transformed my understanding of Schaeffer and his ideas, I do feel like much of his personality is left out of Chion's GUIDE. This is unfortunate given the author's incredible complexity and his contradictions - only the slightest trace of which comes through. To get more of a sense of Schaeffer as a thinker, I very much recommend the collection of essays published by INA GRM back '08 as part of their Polychrome series. It is an excellent read that really fills in the gaps of Chion's GUIDE. But let me recommend that you read the GUIDE first and then go for the Polychrome anthology for the simple reason that the authors in that anthology assume the reader has studied Schaeffer.
Retour sur la Bible Traité des objets musicaux : essai interdisciplines, cet énième livre de Michel Chion revient sur les principes de son maître, son lexique, et plus généralement : sa nouvelle manière d'aborder le musical en partant du concret des sons. Un livre-dictionnaire certes un peu redondant (critique dont il se prémunie dès le départ en pointant du doigt les conséquences de son système de fiches) mais qui a le mérite d'ouvrir les yeux de son lecteur curieux sur le monde sonore qui nous entoure et la cohabitation de ses différents "objets".