The Weight of Water - Anita Shreve

http://www.powells.com/biblio/61-9780316789974-1 - A photographer, Jean, researching the century-old murder of two women travels by boat with her husband, daughter, brother-in-law, and brother-in-law's girlfriend. Jean discovers the long-lost diary of the sole survivor of the brutal crime. As she delves into the narrative, she finds herself engrossed in a tale of jealousy and betrayal - while struggling to keep her own marriage and family together. I enjoy Shreve's books (I recommend The Pilot's Wife) - they are always quick reads with interesting female main characters - great for a long plane ride, or relaxing on a summer afternoon.