How does the author’s framing of the narrative with the Glenmerle location and story affect the overall tenor of the story?

How does the author’s view of death change throughout the story, from his early days with Davy to the end, after her death and the death of Joy (Lewis’s wife)?

What is the “severe mercy” for which the book is named, and how does the concept transform the author’s grieving period after Davy’s death?