The Days I Loved You Most by Amy Neff

Growing up as next door neighbors and friends in the 1940s, Joseph and Evelyn fall in love. Almost sixty years later, they make the decision to end their lives in twelve months because Evelyn has been diagnosed with an advanced case of Parkinson's. Joseph reasons he can't live without the love of his life. Their three grown children--Jane, Thomas, and Violet--are furious with their decision and wish they would change their minds. In The Days I Loved You Most, the story alternates between recounting the many years of the ups and downs of their marriage while exploring how Joseph's and Evelyn's decision has affected both of them and their family.