It was billed as the great "publishing event" of the fall - "a shattering, provocative and mesmerizing true story" so momentous that booksellers ordered copies without knowing what they would receive.
Now, the secret is out: publisher William Morrow has confirmed to The Associated Press that the mystery work is Paul Burrell's The Way We Were, the latest tell-all about Princess Diana by her former butler, who also wrote the 2003 best-seller, A Royal Duty.
"The Way We Were" takes the reader into the lively day-to-day life at Kensington Palace and includes, for the first time ever, a uniquely personal record of that time, according to a statement issued Tuesday by Morrow.
"With previously unseen photographs of the interiors, Burrell takes the reader from room to room, and from memory to memory, in a remarkably candid narrative that only he could tell," the statement said.
Burrell's book, a "follow-up" to A Royal Duty, goes on sale September 12 with an announced first printing of 300,000.