What is the name of the 2016 novel that expands Twin Peaks mythology through a classified dossier?

The 2016 novel is titled The Secret History of Twin Peaks.

Written by Mark Frost, the book is presented as a classified dossier assembled from documents, reports, newspaper clippings, and annotations. An unidentified archivist gathers the material, while FBI agent Tammy Preston examines it and adds investigative notes. The format allows the novel to broaden the history of Twin Peaks beyond the events shown directly on television.

The book covers subjects ranging from strange American incidents and local history to the town’s residents and supernatural mythology. It was published before Twin Peaks: The Return and helped establish background that the revival could develop further.

The title is easy to confuse with Frost’s follow-up, Twin Peaks: The Final Dossier, which was published in 2017. The two books are related but distinct: The Secret History supplies a broad archival history, while The Final Dossier focuses more directly on characters and developments after the original series.