That is a _____ (beautiful) written novel.
The supposed answer is "beautifully" which I understand. But I think "beauty" makes sense as well. It means:
This a novel written by a beauty.
How do you think about it?
No. "Written" functions as an adjective, so it needs an adverb to modify it.
It makes no sense to me to say that a novel was written by a beauty, but even if this is what you wanted to say, this is not how you would say it. If a novel had been written by a Frenchman, for example, you could not say "This is a Frenchman written novel".