Someone told me about this edition for Chopin's Fantasie Impromptu in C# minor Op 66. It's edited by Maurice Hinson and includes Chopin's original manuscript as well as the Fontana edition.
The Foreword includes the context in which the FI was composed, notes about the Fontana edition, and notes from Hinson about performing his piece and practice techniques. I plan to write more about this book and Hinson's notes in my blog soon.
The main differences between Chopin's original ms and the Fontana version is in bars 13 - 24. In the Fontana version, you have the thumbs accented for bars 13 - 16, then the 5th finger accented for the off beats from bars 17 - 24. The original has no accents but the first note of each 16th note group is held as a quarter note. There are other differences as well.
Since Arthur Rubenstein was mentioned as the Chopinist in this book, I found his YouTube performance of this piece, which was of the original version:
In Hinson's opinion, this piece is usually played too fast, as an exercise in velocity rather than as the poetic expression of two contrasted moods - that of the Allegro Agitato and a broadly lyrical middle section.
This edition may be purchased here: