Candace Fleming’s latest book has the elements of an overheated dystopian thriller — political repression, malevolent figures, a protracted war, endangered children — but no prospect of a triumphal ending. Focusing on the last czar and his family, Fleming, who has also written books about Amelia Earhart and the Lincolns, delivers another engaging and insightful work of history, giving young readers a clear sense of the complicated world in which the Romanov family lived and died.