The Second Coming: A Novel by Walker Percy

Will Barrett (also the hero of Percy's The Last Gentleman) is a lonely widower suffering from a depression so severe that he decides he doesn't want to continue living. But then he meets Allison, a mental hospital escapee making a new life for herself in a greenhouse. The Second Coming is by turns touching and zany, tragic and comic, as Will sets out in search of God's existence and winds up finding much more.