Trying to find a book that matches something I thought of

So I was just thinking an suddenly I thought of a situation where the MC is wanting to write a book about a killer but they want to write it in the perspective of the killer and so they figure out a way to do that and then I was thinking about how that could be a good dark romance book and now I wanna know if there is a book with that plot so I came here for answers

Edit: bonus points if they were the killers next victim