Not sure if this already has been suggested/asked, but there is the section in the manga info about how much of it has been adapted into an anime (Anime Start/End Chapter).
Would it be possible to add a section detailing how much of a novel/anime/movie/whatever has been turned into manga?
Example: Asobi ni Iku yo! (Novel) has 20 Volumes and Asobi ni Iku yo! has 10. How much of the novels are adapted into manga?

~4400 manga completed
~1700 ongoing...

How about just adding such information to the description section? After all, you would outline what to expect from an adapted manga without spoiling too much, which virtually is the definition of the description section.

(ㆁωㆁ*)