I am a great fan of Robert Harris's fiction but this was my first of his nonfiction books and it did not disappoint. The book tells the incredible story of how a rather  lazy and greedy journalist at a German magazine in the 1980s is convinced that Hitler had written a series of personal diaries and that these had been recovered from a plane crash and were being smuggled out of east Germany. His magazine hands over millions of marks for the purchase of the diaries with plans to publish them in a series of articles. The story of greed and ineptitude unfolds very slowly (at time agonizingly) to the eventual testing of the material by real experts in Hitler's writing and forensic testing of the materials. 
I must say it took me a long time to read this book with many intervals, but I am glad I read it.