This was quite a fascinating read. The authors present their experience in minute detail and explain the research they painstakingly carried out over a decade in their attempt to get to the bottom of what happened. As the book progresses, the reader comes to appreciate how from their point of view, what they experienced is truly inexplicable. I liked how their quest for answers led them to dig for and uncover more and more historical information that slowly painted a picture of Marie Antoinette's life and connected the dots between the various seemingly unimportant details of what happened that day, leading them to understand the significance of certain things. Regardless of the reasons behind the mysterious events, they gained a unique perspective of this slice of history. For that reason, it's an interesting read for anyone trying to learn more about the French Revolution.
Their effort is admirable, especially when you compare how much easier it would be to do the same research today with the benefit of the Internet and easy remote communications. As it was, it being 1902-1910 they had to hunt down people who knew people who had heard stories, visit libraries and pore over dusty old maps in bookshops. And since they lived in England, they often could do this research only during their trips to France.
The average reader may find this book a bit dry, since after the initial presentation of the events the authors go into extraordinarily detailed explanations of their research and the events are examined from many angles (creating a sense of repetition). It should be remembered that they approached this in part from an academic perspective.
Most of all, I enjoyed the very interesting conclusion they ultimately drew in their attempt to explain this apparent slip in time.
The one downside to this book, as other people have commented, is that large sections of French quotes are included but without any translation. Maybe back in 1911 the average educated English person could read French, but this could be frustrating for the non-French-speaking reader of today. For me it was fine because I luckily can understand French.
I read the public domain version of this book online (first edition published in 1911 under pseudonyms) so can't comment on any additional information that may be included in this particular edition.