Yes, I have that book and it is excellent. I really hope the book that Cay refers to becomes available in English. Or, maybe it's just a repeat of the Becker/Warter book?
What is not a repeat is the new edition of
Porsche: Excellence Was Expected. It came out September 1, 2003. It is a large three volume set chronicling Porsche history through 2002. It has very detailed background on the Cayenne and Carrera GT development. We speculated recently on the reason Porsche and Mercedes broke off their SUV development program. In volume three it is revealed that a Mercedes representative proposed in a meeting that Mercedes needed some ownership in Porsche for the project to go forward. At that point Wiedeking stood up, called the meeting and all negotiations off and walked out. End of story. Here is a link to the publishers website:
web page. You can also order it from Amazon for considerably less.