UNTERSUCHUNGEN ZUR MUSIKALISCHEN SPRACHE VON FRANK ZAPPA

• rebell, komponist, genie: untersuchungen zur musikalischen sprache von frank zappa
  by stefan ullmann
      (2019, book, --, books on demand / private release) - november 2019

In German.

The last couple of years, Stefan Ullman has made several books available discussing Frank Zappa's music. Some of these are translations, others are re-issues with a different cover.
If I'm not mistaken, the above pictured book is a re-issue of :

It takes a closer look at FZ's 'The Black Page no.1' and 'Inca Roads'.