C. S. Forester 
The Good Shepherd [EPUB ebook] 

The Good Shepherd has been adapted into a 2020 major motion picture called Greyhound for Apple TV+. It was scripted by and starring Tom Hanks.
The hero of The Good Shepherd is Commander Krause, the captain of the fictional US Navy Mahan-class destroyer USS Keeling in World War II. Krause is in overall command of an escort force protecting an Atlantic convoy in the Battle of the Atlantic, shepherding it through the Mid-Atlantic gap where no antisubmarine aircraft are able to defend convoys. He finds himself in a difficult position. The voyage in question occurs early in 1942, shortly after the United States’s entry into the war. Although he is a career Navy officer, with many years of seniority, this is Krause’s first wartime mission. The captains of the other vessels in the escort group are junior to him in rank, and much younger, but they have been at war for over two years.
The story covers 13 watches (52 hours) aboard the ship’s bridge and is told in third person entirely from Krause’s point of view as he fights to save his ship, detailing his mood swings from his intense and focused excitement and awareness during combat to his resulting fatigue, depression, and self-doubt as his self-perceived inferiority and inexperience to the other captains under his command troubles him (although as the story progresses he is shown to be quite capable). He broods over his career and the wife who left him, partly because of his strict devotion to duty. He is troubled when the press of duty forces him to neglect his prayers (unlike most of Forester’s other heroes, Krause is devout). He is troubled by recollections that the Navy review board had twice passed him over for promotion, returning a judgement of fitted and retained due to little or no opportunity in the prewar Navy. His promotion to Commander only came when the United States entered the war, leading him to fear that he may be unsuited to his command.