Fascinating story but long winded

Don't ask why but I'm a huge fan of books that tell the story of people's lives and how they were affected during WW2. Naturally when I heard about this story I couldn't wait to read it. I really enjoyed the story as it gave me an insight into the details and history of the Nazi ideology that I hadn't really thought of before. I found myself fully engrossed in the chapters about the actual story and main characters, but, found myself bored in the chapters that to me were unnecessary and over detailed, with reels and reels of background information about characters who were not integral to the plot in my opinion. I found these tedious and found my concentration slipping away. I'm not one to not finish something I start reading and thankfully the chapters I was engrossed in were enough to keep me interested.