I’m looking for a word that may or may not exist. The German word for a comic adapted to a film is Comicverfilmung (for regular books it’s Buchverfilmung). I am looking for the word for a book adapted into a comic, for example the graphic-novel versions of the Game of Thrones book series. I have had no luck so far, and am now just hoping that there is a word for it. Also, if not how would one go about saying that there is a comic version of a book?
The first word that came to my mind was Comic-Version - and indeed: Amazon gives some dozens hits for this search term that appear to be the kind of comic you are after. The term itself does not communicate that the original was a book, so you'd have to put this in the phrase if needed, like "Comic-Version eines Romans von X.Y." or "Comic-Version von Krieg und Frieden".
Adaption works for almost anything, but just includes the target medium – or, ambiguously, the source medium. You would include the original medium as a genitive attribute: Filmadaption des Romans, Musicaladaption des Videospiels, Bühnenadaption des Dramas … In some cases, Version works, too, but it somewhat assumes equal authoritative status of several versions.
The word also describes the actual relation much better, usually, because the medium shapes the content, i.e. many parts are omitted, added or changed (“re-imagined”).
If you’re looking for a less foreign term, native Umsetzung is also an option: Comicumsetzung.
I'll throw "das Comic zum Buch" in the ring.
I ran a search and found an article:
Jetzt haben sich zwei Comic-Autoren daran gemacht, das mehrfach ausgezeichnete Werk als Bildgeschichte umzusetzen. Mit Erfolg: Der Szenaristin Gerlinde Althoff und dem Zeichner Christoph Heuer ist eine beeindruckende Adaption des Klassikers gelungen.
"Umsetzung als Bildgeschichte" sounds a little bit more exalted than "comic", and "XY als Bildgeschichte" might be more fitting, depending on what XY is.