Writing Characters From Real Life: Better To Know More Or Less?

      I just finished reading Nothing To Be Frightened Of, an intelligent, witty musing on death and dying, by the British novelist Julian Barnes. To quote noted children's author Peg Kehret, "He is funny and thought-provoking at the same time, and he does it all with such glorious language." The book is also a memoir, featuring stories about the author's family and friends which influenced and inspired his thanatopsis. And especially in the final pages, Barnes brings to the fore some thoughts about the ways and means of fiction writers.
      One of these thoughts is that in basing fictional characters upon real people, an author is wise to not know too much about the source. Barnes tells about a writer-friend who eavesdrops on conversations, but is careful to walk away from the speakers before he's been overexposed, and therefore limited in developing his characters.
      At first, I agreed with Barnes. I've been unable to use people I know as characters in my books, because as a seat-of-the-pants writer whose characters and plots develop during the course of the first draft and beyond, knowing all I do about my friends and acquaintances seriously restricts their fictional development. There are things these people simply will not say or do on a computer screen.  
      For this reason, when I set out to write my history-based ragtime mystery trilogy, I was leery of over-researching people like Scott Joplin; his publisher, John Stark; and Brun Campbell, the Ragtime Kid. But as I went along, I found the more I learned about a particular person in history, the more possibilities opened for characterization and plot. Without having a first-hand take on someone whose life I knew was over, all the information I gleaned from historical documents set itself up as a supporting structure, and the more extended that structure became, the more compatible fiction the character could build upon it as my story developed.
      One post-facto example: Nan Bostick, a ragtime pianist/historian/composer from the San Francisco Bay Area, is the great-niece of Charles N. Daniels, a prolific composer and publisher from the Ragtime Era and beyond. After Nan had read The Ragtime Kid, she told me she'd enjoyed the book, and had loved seeing Uncle Charlie as a character. But I wish you'd talked to me about him, she said. At one point, your Uncle Charlie said, 'Goddamn,' but my Uncle Charlie never, ever, used profanity or blasphemy. And during a heat wave in Sedalia, your Uncle Charlie loosened his tie and opened his shirt collar. My Uncle Charlie wouldn't have done that. He used to drive his wife crazy by going fishing in a properly-set up white shirt and tie, and his best wool suit. 
      Not that I thought my knowledge deficit had done my book mortal harm, but had I known about those quirks, my picture of Uncle Charlie might have been that much more arresting. And beyond that, Uncle Charlie's real-life peculiarities might have made the plot an even richer stew. I have to think, in historical fiction, more background information, used judiciously, is never going to be less.