Ackerman uses the Author’s Notes primarily to explain how she did research for The Zookeeper’s Wife long after both primary characters had died. She interviewed several people who had lived in Warsaw during the Nazi occupation, including the Żabińskis’ children, Ryś and Teresa. She exhaustively researched the social, ecological, religious, and political environment of the war era. Most importantly, she used the primary resources of Antonina’s diaries as well as books, journals, and letters from both Jan and Antonina.

The author introduces the two main characters: Jan the director of the Warsaw Zoo, and Antonina, his wife. They meet at the Academy of Fine Arts, where each expresses a love of nature and animals. Antonina is the daughter of a railroad engineer who traveled through Russia. A very plain-spoken man, he and his wife were shot by the Bolsheviks during the Russian Revolution in 1917. After her father’s death, Antonina went to Uzbekistan to study piano and then to Warsaw to study languages. She and Jan marry in 1931.

The zoo is a new endeavor for Warsaw, though most of the major cities in Europe began developing zoos in the early 20th century. Jan jumps at the chance to become the second official zookeeper.