Good call there ...James Runcie: The Road to Grantchester.
A great deal more than merely, as the author suggests, a 'prequel' to his six books of 'cozy' detective fiction.
The central characters journeys from personal angsts to religious faith, and enters the Anglican priesthood, with continuing doubts and conscientious difficulties. The first third is a harrowing account of the war in Italy, from Salerno to Monte Cassino, and on to the Po Valley.
It is a far, far stronger novel than anything else from Runcie.