How does the author of Parallel Journeys make distractions between Alfon's experience and Helen's experience?

The author structures the book by chapters, which are dedicated alternately to Alfons' and Helen's stories. In doing so, Ayer gives the reader a sense of what is happening to each of them in their opposite places during the same war. One example of this can be found in the anti-Semitic attacks suufered by Helen's family, as opposed to Alfons training as a soldier in the Hitler Youth. Each chapter moves the story along from the alternating perspectives of Alfons and Helen.