The fact that the screenwriter nor the author ever met Mr. Oskar Schindler or Amon Goeth is an important element in the story of what actually occurred during this part of history. The novel and the screenplay were totally based on people's experiences and memories of their interaction with Mr. Schindler during this time. There is no way we can really be sure that Mr. Schindler's motives, actions, or activities were actually true to the way they were portrayed in the novel and movie. We can base our opinion and reactions to this story by having empathy for the survivors who told his story but we can not consider this to be an actual authorized biography of Mr. Schindler.
It is important to recogonize that Kenneally is very honest about this at the beginning of his book and the book is written as the story of the survivors not really a biography of Schindler. The movie is, as most movies are, very liberal with the facts and the drama of Schindler's life and is not as accurate as the book.