Great in depth biography of Sisi, with many quotations from the source material. However, Hamann's biases are glaringly obvious throughout the book, making it a difficult read at times. She also, at multiple points, makes assumptions about Sisi's and other people's thoughts, feelings, intentions and motives without giving any sources that substantiate these conclusions. Recreating the life of an enigmatic person like Sisi is difficult, but when one states mere assumptions about things as personal as inner thoughts as fact without having concrete proof of these claims, it smells more of the projection of the author's own feelings onto a historical character than of fact.
All in all, a good biography to get the facts of Sisi's life and those around her, but take any other "conclusions" about Sisi's mental state, feelings, etc with a large grain of salt.