Hermann Nitsch, The Gesamtkunstwerk of the Orgien Mysterien Theater, published in 2015 by Verlag der Buchhandlung Walther König. Insanely huge art book of 968 pages, if you're into Hermann Nitsch this is the document. It's an incredible tome covering all of his work from the actions to the paintings and drawings, theater and opera staging, even his musical scores. There are essays by Nitsch and others throughout and a whole section devoted to some of Nitsch's key texts on the philosophy of his work. There is a German version and an English version, it looks like the English version might be out of print. I got mine off AbeBooks for a reasonable price. Definitely worth it if you're really into this.
"In addition to functioning as a substantial documentation of his work and in a sense preserving and disseminating it, it was important to me that this book should reflect the artist's own style of editorial and graphic work. The artist Hermann Nitsch should help shape and design his reference work, so that it captures his Gesamtkunstwerk for posterity in a way that is authentic, genuine, and entirely in the artist's spirit. The focus of this extraordinary book project was not just a monograph on Hermann Nitsch but a monograph on and by Hermann Nitsch. A magnum opus on his magnum opus." -Michael Karrer, Editor
German Edition ISBN 978-3-86335-702-3
English Edition ISBN 978-3-86335-703-0