What I liked most about this book was Alenka, a character who appeared late in the novel. She was spirited, resourceful and optimistic in a situation that left little room for optimism. She played an important role in Cargill's version of the Warsaw Ghetto Uprising. I also found her believable unlike the nine year old protagonist, Abigail.
Another review said that Abigail became unbelievable only toward the end of the book during the uprising. I disagree. I think she was always too good to be true. She had no flaws other than being young and innocent which was too temporary in her horrifying environment to be a real flaw. All the children in the Warsaw Ghetto had to grow up in a hurry. Abigail became much more seriously unbelievable toward the end of the book. She not only acquired skills too quickly, she was better at them than anyone else. Credibility went out the window.
I should state at this point that I took a course on the Holocaust from the Jewish Theological Seminary. One of the books I read in that course was The Theory and Practice of Hell by Eugen Kogen who was a political prisoner in Buchenwald. I am mentioning this so that readers are aware that I have also read books from the perspective of non-Jewish Holocaust victims.
Kogen's book shows that the Nazis were quite rigorous about separating non-Jewish prisoners from Jewish prisoners. The Nuremberg Laws actually required them to make sure that Jews had no contact with other types of prisoners. They were afraid of "race pollution". Separation of Jews from non-Jews was also the main reason for their establishment of Jewish ghettos like the one in Warsaw. So they wouldn't have deliberately sent someone who was legally non-Jewish to a Jewish ghetto. From the Jewish perspective, they did send quite a number of non-Jews to Jewish ghettos. This is because the definition of who is a Jew according to Jewish law was more restrictive than the Nuremberg Laws.
I am bringing up this issue because there is a character in this book who was sent to the Warsaw Ghetto even though he was non-Jewish. This may seem like a minor point to other readers. He was portrayed very movingly and I liked the role he played in the novel, but it bothered me that the author didn't understand something very basic about the Nazi mindset.
Cargill also mentions Israel a few times. Israel didn't exist until 1948 which was after WWII. There is a statement made by a character in this novel that the Warsaw Ghetto Uprising was partly funded by "our friends in Israel". This is highly improbable. At the time, Jews in America were sending funds to Palestine to help with the struggle of Jewish settlers against the British Mandate. For more information see the article on the Jewish Insurgency in Palestine on Wikipedia.
I'm picky about the historical details discussed above because they matter to me. They probably wouldn't even be noticed by many readers.
From a storytelling perspective, I thought that Saying Goodbye To Warsaw was well-plotted and well-paced. I also liked the final scene. It affirms the centrality and sacredness of family. In the end, family is what matters most.