50 Children: One Ordinary American Couple's Extraordinary Rescue Mission into the Heart of Nazi documents the little-known story of Gil and Eleanor Kraus' successful mission in 1939 to rescue 50 Jewish children from Nazi Germany on the eve of war and bring them into America at a time when the U.S.'s immigration laws were at their strictest.
Steven Pressman first made a documentary film about this story which aired on HBO titled: 50 Children: The Rescue Mission of Mr. and Mrs. Kraus, which he wrote, directed, and produced. Pressman then decided to write a book because so much of the details from the interviews with surviving children, an unpublished memoir from Mrs. Kraus, documents, photos, etc. did not make it into the film. The book expands on the political conditions at the time and paints a fuller portrait of the couple from Philadelphia, Gil and Eleanor Kraus.
It should be noted that there had been other rescues of children in the early days of WWII, such as the Kindertransport to Great Britain, but this was the largest single transport of Jewish children to the United States, which clearly shows America's failure to act more compassionately toward refugees.
If you would like to learn more about other rescues of children during WWII, I recommend Rescuing the Children: The Story of the Kindertransport by Deborah Hodge and Saving the Children from the Holocaust by Ann Byers.