We Shall Not Sleep by Anne Perry

This is the final book in a five book series that began the day the archduke and duchess were shot and world war began. The series is about siblings Joseph, Matthew, Hannah, and Judith Reavley, whose parents are killed the same day as the archduke. They were murdered to keep John Reavley from telling what he knew of a diabolical plot. As the war progresses, Joseph and Judith end up at the front--Judith as an ambulance driver and Joseph as an army chaplain in the trenches, Matthew stays in London in the Secret Service looking for the mastermind of the plot--a man they call the Peacemaker, and Hannah moves back home, bringing her children while her husband commands a navy ship.

Perry is a wonderful storyteller, making the reader feel as though they are there. In addition to the war background, each book has a mystery that must be solved. The books, in order, are: No Graves As Yet, Shoulder the Sky, Angels in the Gloom, At Some Disputed Barricade, and We Shall Not Sleep. I highly recommend this series--in fact, I plan on re-reading it in the near future. While Perry does a good job with back story, I want to read them all in order to keep characters and events all in my head.