What separates this biography from others is Popoff’s access to a trove of unpublished material, including a memoir and countless letters that have been locked away in a vault in Moscow. The memoir, in particular, adds rich detail to what has long been known about Sophia Tolstoy from her brilliant diaries, which were translated into English in the mid-1980s. We learn, for instance, that because her father had sired several children out of wedlock, Sophia feared she herself might not be legitimate. (To prove otherwise, she forced him to produce her birth certificate.) After learning more about her early years, one suspects that in marrying Tolstoy she was reproducing some unhappy but familiar family dynamics.