The X4: Foundations Collector's Edition Content includes:

• Access to the first two expansions for X4: Foundations: (2020) and (2021)
  
• The X Universe Digital Artbook 2018: Enjoy the concept art behind the X universe.
  
• X Novel: Nopileos by Helge Kautz as English and German eBook.
  
• Digital Soundtrack: Download the music, including exclusive versions of the trailer and teaser music in highest possible quality, for X4: Foundations, X4: Split Vendetta and X4: Cradle of Humanity.
  
• X Encyclopedia

The bonus content will be placed in your X4 installation folder:
...Steam\SteamApps\common\X4 Foundations\Bonus Content