Strangely, it is now possible to add this content to the library, even without owning the base game.
There's an interesting comic and a book.
https://store.steampowered.com/app/1495710/
Digital goodies included:
- Original score
- Art booklet featuring a selection of art from the game
- Digital Comic "Cyberpunk 2077: Your Voice"
- Cyberpunk 2020 sourcebook
- Wallpapers for desktop and mobile
Base game is not required to claim the package.
After claiming it appears in the soundtrack section.