There are a few possibilities:
* Diana Douglas (1923-2015) was an American actress, known for her roles in movies like "The Big Sleep" and "The Glass Menagerie". While she acted in many projects, she did not write any books.
* Diana Douglas (1923-2015) is also the mother of Michael Douglas.
* Diana Douglas (1923-2015) is also the former wife of Kirk Douglas.
If you are thinking about a different Diana Douglas, please clarify.
Could you please provide more context about the Diana Douglas you are interested in? This would help me to find out if she is a writer and what she has written.