Addedum

 I'm laughing at myself.  Less than an hour ago, I went to post my review of The Sleeping Witness by Fiorella de Maria, on Goodreads, and found out that I read this book a couple of years ago! I would have given the book the same score. 

My First Father Gabriel Mystery

 The Sleeping Witness by Fiorella de Maria is my first Father Gabriel mystery.  Like Brother Cadfael's mysteries, Father Gabriel is a Benedictine monk.  I guess Benedictines have more freedom than your usual run-of-the-mill monk, because these two are always investigating murders outside the monastery.

Whatever happened to a monk's vow of stability?

The setting is important in the story.  I don't mean the place.  I mean the time--right after War II.  The people are affected by that war in many different ways, and I don't necessarily mean by being directly in it. Those that were directly involved, came home.  Therein lies the devil.  Everyone is damaged.

The wife of the local doctor was beaten into a coma.  She was in the concentration camp.  Her husband found her in the camp and nursed her back.  The murder victim was a camp guard in her camp.  The husband is the obvious perpetrator, but Father Gabriel keeps digging deeper.

Introducing Father Gabriel

 This is a Who Done it Mystery! The Sleeping Witness by Fiorella de Maria solves a murder. The detective is a Benedictine Priest, named Father Gabriel. Two acquaintances from a concentration camp meet again, many years later. One, almost two, are murdered. The arrested husband of one of the victims turns out not to be the killer. That's not really a spoiler, because the first arrested in mysteries is never the real murderer.

WWII is involved; I actually learned a few facts. Only in Auschwitz were concentration numbers used. Also, war continues long after a peace treaty is signed.
I found the trail of evidence convoluted, and the suspects confusing. This is why I only gave the book an average rating.