A Fine Summer's Day by Charles Todd

If you're a fan of the Inspector Rutledge series, as I am, you will be delighted to discover A Fine Summer's Day, which gives the back story of Inspector Rutledge before he goes off to fight in World War I. We learn more about his one-time fiancee, Jean, and his beloved sister, Frances. We even get a glimpse of Hamish MacLeod, who plays such a big part in Rutledge's life after the war. It's an excellent companion piece to the rest of the series.