Chris Jarrett's translation of Wolfgang Sandner's book has been published in November 2020 by Equinox Publishing.

Few writers have come as close to Keith Jarrett as Wolfgang Sandner, who has not only closely followed Jarrett’s remarkable career from the 1960s, but has also had the opportunity to visit him in his home in the United States. For this biography, which is full of detailed musical analysis and cross-references to other artistic genres, Sandner has collected new information about Jarrett’s family background, much of which is thanks to the translator, Keith Jarrett’s youngest brother Chris. The book explores Jarrett’s work with other musicians, in particular the members of his American and European Quartets and his Standards Trio, it charts the development of his solo concerts, and it also investigates his work in the classical sphere, as well as the highly original music he has created in his own home studio. It also covers his associations with his various record labels and producers, notably his unparalleled relationship with ECM and its founder Manfred Eicher. This English edition is a significantly extended and updated version of the German original.

Thanks to Chris Jarrett for letting me know. I somehow totally missed it!