Killers of the Flower Moon: The Osage Murders and the Birth of the FBI by David Grann, 320 pages

In the 1920's the Osage Indians of Oklahoma were quite wealthy.  Their land was oil-rich and they owned the mineral rights.  All was not rosy however.  Dozens of Osage Indians were murdered and somehow those cases couldn't be solved locally.

Finally, the Bureau of Investigation stepped in and found out who was behind at least some of the murders.  The why was easy - greed. 

In the first part of the book, author David Grann explores the story of one of the families whose members were murdered.   The second part details the investigation into the murders by the Bureau of Investigation, which became the Federal Bureau of Investigation.  The third part details the authors own investigation into this story, the additional information he found and the closure he was able to provide to some of the families whose relatives were murdered.