This Book refers to Suicide is Painless performed by Johnny Mandel
Nick hears Amy singing the theme song (Suicide is Painless) to the television series 'M*A*S*H' while making breakfast on their anniversary. (Page 7)
Gone Girl takes up the story of Nick and Amy Dunne's difficult marriage, which is floundering for several reasons. Nick, a former journalist of some seriousness, loses his job due to downsizing. In a somewhat desperate state of mind, he relocates himself and his wife from New York City to the small Midwestern town of North Carthage, Missouri, where Nick is from. There, he opens a bar, using the last of his wife's trust fund, and runs it along with his twin sister Margo. The bar provides a decent living for the three Dunnes, but the Dunne marriage becomes more and more dysfunctional. Amy loved her life in New York and hates what she considers the soulless "McMansion" which she and Nick are now renting.