This happens to every author. A person approaches and begins to tell you what you should be writing. It's never what you are known for writing. Usually, they suggested their memoirs or family stories, but sometimes not. I recently took a long vacation by train. During the trip, a window popped out of one the cars. We were sidetracked, literally, until the police could arrive and determine if our train has been shot at. During the long interval, several of my fellow travelers suggested I write a mystery where someone is shot on a train. They were willing to be in the book. Of course, I told them at the beginning of the trip that I wrote romance novels and some historicals. Sure, this story would be great - if Agatha Christie hadn't already written Murder on the Orient Express. Still, some of the tourists were interesting enough to make great characters in any book.
The saddest incident I ever encountered was when a Holocaust survivor approached me about writing her story. I was still working full time as a librarian, had a family to care for, and very little writing time. I urged her to record or write down her own memories for her family to cherish. To create a book from her story would have required hours of fact checking and historical research, time I did not have. Eventually, she did tell her story to the local paper and perhaps that sufficed.
Some have said I should write my autobiography. Believe me, although I speak vividly about parts of my life, it would not be of wide spread interest. No abuse, drug use, or murders occured. I had a pretty typical small town upbringing and do use bits and pieces of it in my fiction, but an Oprah Book Choice it would not make.
Not that I am without guilt in this area. I once told well-known author, James Lee Burke,that he should write a mystery taking place in our local Laotian community. He gave me the standard polite answer. "You should write that story yourself." Which when this started happening to me, I felt free to borrow. However, I do doubt I will ever write a hardboiled dectective novel that takes place in our Laotian community. It's still a great idea. Someone should do that.