Just before the turn of the millennium, Rocco di Pietro held several interviews with Pierre Boulez, focusing on the eminence grise's compositions and teaching (if you like Boulez only as a conductor, there's nothing for you here). This book started when Rocco di Pietro ambushed Boulez for a few brief comments, but Boulez was impressed with the questions he asked, and so further interviews were given.
Indeed, Boulez is remarkably forthcoming here. There's quite a bit of information I've never seen elsewhere, for example why Boulez stopped conducting Maderna (the scores were illegible and there was no critical edition). While it is generally known that Boulez wanted to write an opera, here he talks in detail about the musical and dramaturgical qualities that he wanted to explore, as unlikely as a Boulez opera looks now. "Anthemes II" gets a comparative enormous amount of description by the composer, especially the work's electronic part, and a few facsimiles of the manuscript are presented.
It's always fun to hear Boulez rag on other composers. Many are aware of his quip that Shostakovich is just a "second- or third-pressing of Mahler", but here he disses many more composers: "You know, these kind of anarchic people, they are needed from time to time, because they are subverting the kind of academism to which everybody finally tends. But, as values, these people's ideas have no values. I put in this category Satie, Ives, Cage; I put Scelsi and I put Feldman -- people who are provoking thoughts, but who have not the tools to realize their ideas."
There are some typos in the work, and since this is a collection of talks from separate occasions, there's a little repetition. So, DIALOGUES WITH BOULEZ is not perfect, but I think any fan of the composer would enjoy this book.