Koppel began contributing by reporting to The New York Times Boldface Names celebrity column in 2003.
Koppel's book The Red Leather Diary: Reclaiming a Life Through the Pages of a Lost Journal was published by HarperCollins on April 1, 2008.
The book is about her discovery of a young woman's diary, kept in New York in the 1930s, and its return to Florence Wolfson Howitt, its owner, at age 90.
The diary was recovered from a steamer trunk found in a dumpster outside of Koppel's apartment building on the Upper West Side of Manhattan.
[3] The book served as the basis for the ABC short-run TV series The Astronaut Wives Club, which premiered in June 2015.