Robert Graves in the Great War (2018)
fantastic-writers-and-the-great-war.com
fantastic-writers-and-the-great-war.com
Richard Holmes writes well about the trench warfare in "tommy", using sources like surgical & medical notes.
Pat Barkers "regeneration" trilogy from 1991 is about (amongst others) Sassoon, Graves, Owen, and the psychologist who treated Sassoon in Edinburgh. WHR Rivers was an interesting man in his own right. It's fiction but beautifully researched and written. I would not personally call Craiglockhart "outside" Edinburgh, it was a developed suburb of the town even in those days I think. Maybe the conurbation was less dense then.