The book is "The last Courts of Europe. A Royal Family Album 1860-1914". But Robert Massie only wrote the introduction. The picture research and descriptions are by Jeffrey Finestone.
THe photo is spread in pages 88-89, and the description says "Empress Elisabeth on her deathbed, 10 September 1898. She was assassinated at Geneva while boarding a boat - stabbed in the chest, she nevertheless continued walking but collapsed some moments later".
The photo was reproduced by permission of Roger Violet, Paris.
I hope this helps ;-)