The Open Library entry tracks various editions and provides "Borrow" links to the Internet Archive.
Rolf Wiggershaus died in 2019. His works are under copyright protection in most countries (70 years after the author’s death). In Brazil, the Lei de Direitos Autorais (9.610/98) protects the work until 70 years after January 1st following the author’s death (i.e., around 2090).
Would you like help finding a library near you that holds the physical or digital copy?
You're looking for a detailed write-up on Wiggershaus' "The School of Frankfurt" (Die Frankfurter Schule) in PDF format, and preferably for free. Here's what I found:
Rolf Wiggershaus does more than just list dates; he provides a "critical historiography" that connects the personal lives of the thinkers to the evolution of their ideas.