I think Ms. Erickson's book Alexandra reads more like fiction rather than a real biography. I wouldn't rely on it very much for facts.
In the mean time, I have found a longer storyline and put in some of the advanced praise for The Tsarina's Daughter:
From the bestselling author of The Hidden Diary of Marie Antoinette comes a dramatic novel and powerful love story about the last Russian imperial family.
It is 1989 and Daria Gradov is an elderly grandmother living in the rural West. What neighbors and even her children don’t know, however, is that she is not who she claims to be—the widow of a Russian immigrant of modest means. In actuality she began her life as the Grand Duchess Tatiana, known as Tania to her parents, Tsar Nicholas II and Tsarina Alexandra.
And so begins the latest entrancing historical entertainment by Carolly Erickson. At its center is young Tania, who lives a life of incomparable luxury in pre-Revolutionary Russia, from the magnificence of the Winter Palace in St. Petersburg to the family’s private enclave outside the capital. Tania is one of four daughters, and the birth of her younger brother Alexei is both a blessing and a curse. When he is diagnosed with hemophilia and the key to his survival lies in the mysterious power of the illiterate monk Rasputin, it is merely an omen of much worse things to come. Soon war breaks out and revolution sweeps the family from power and into claustrophobic imprisonment in Siberia. Into Tania’s world comes a young soldier whose life she helps to save and who becomes her partner in daring plans to rescue the imperial family from certain death.
It has received some praise as well! By Publisher's Weekly:
"A top-notch narrative …Erickson creates an entirely convincing historical backdrop, and her tale of a family’s fall from power and a country in transition is both romantic and gripping.”
And by Library Journal:
"Erickson weaves historical details into this imaginative account of how Tatiana Romanov . . . escaped the Bolshevik assassins who killed Russia's royal family in 1918. . . . Despite knowing the real Tatiana's fate, readers will rejoice in the fictional version's survival. A sure winner for public library fans of historical romance."