Every Man Dies Alone by Hans Fallada
This book was based on an actual Gestapo file.
Fallada was given the file after the war by a friend and after reading through the entire file, he sat down and wrote a fictionalized version of the story in about 24 days and 539 pages.
This was a very engaging story about a couple living in Berlin during World War II. They voted for Hitler the first time but later became disillusioned by his regime. After their son is killed in the war, they decide they must do something to speak out against the lies and propaganda of the Nazi regime.
This is the story of their day to day lives and the lives of those people who are geographically close to them. Because of this, these others become embroiled at some point or another in the saga. It is a tragedy many times over.
This was an excellent book and I highly recommend it.
Fallada wrote quite a few other books and it looks like they have all been translated into English.