The story is narrated by Maria, in bits and pieces as she jumps forward and back through time. If you are reasonably familiar with the story of the last of the Romanovs, it's not particularly confusing, but I can see that it might give you trouble if you're not. As far as I can tell, most of the historical information is accurate, but Harrison has infused the book with her own whimsy, inventing fanciful conversations between Maria and the young Alexei (or "Alyosha" as he is called by Maria), and even a bit of youthful sexual exploration. It is a novel, after all.
Rasputin did have a daughter named Maria, who, I have learned, did survive the Bolsheviks and later became a lion tamer in Europe and America, even working for Ringling Brothers at one time. She also wrote several memoirs about her father, one of which I am currently trying to track down.
We all know the horrifying story of the fate of the Romanovs, and this book did little to add to that knowledge, but I found Harrison's treatment of Maria's memories of her enigmatic father (which I suspect are based on Maria's memoirs) to be the most interesting part of the story. I also enjoyed the tales she told to Alyosha. They have that dreamy air of fairy tale mysticism that seems so characteristic of much Russian literature. Harrison's treatment of Alexei's budding sexuality, on the other hand, seemed crass and unnecessary.