Why are mystery novels almost always murder mysteries? With myriad mysteries to be explored — of belief, relationships, disappearance, origin — why do many writers and readers fixate on the black-and-white clue accumulations of the murder mystery? 

“There’s less gray zone there so there’s less moral ambiguity about a murder,” muses Canadian CBC journalist-turned-bestselling-novelist Louise Penny, author of the Chief Superintendent Armand Gamache mysteries. “My books are clearly murder mysteries, but there are also a whole lot of other mysteries — the mystery of life.

“I think this is a real golden age right now of the mystery novel, and I think the way to say it is not ‘crime novel,’ not even ‘murder mystery.’ The mystery novel is enjoying such a resurgence because I think great mystery novels are about the moral ambiguity of it all.”

Murder propels the action in the 59-year-old writer’s newest addition to the Gamache series, “Glass Houses,” a suspenseful, elegantly written page-turner that this writer read in one sitting. But the book’s rewards go well beyond a whodunit’s jigsaw pleasures (although those are considerable). Within the twisty contours of Penny’s unpredictable plot, she thoughtfully examines the idea of a court of conscience. Its relevance to current sociopolitical climes is unmistakable as relatable characters heed the dictates of what they consider a “higher law” — and confront the consequences.

“It’s not as simple a question as it appears on the surface,” Penny says. “You think, well, conscience is a good thing. But as I talk about in the book, so many horrific acts are committed in the name of conscience.

“The book is about a crime, but that’s the starting point, not the final point. All the themes are about us as human beings and the choices we make, not necessarily to break the law but to justify our daily acts, some of which are beautiful and some of which are ugly. But we hide behind the idea of ‘I have a moral right to do this.’ And you see what’s happening in the world. It’s uncomfortable because many of these people genuinely believe that they are in the right; that they have a moral obligation to do what it is that they are doing. And the rest of us disagree. It’s so interesting when consciences clash. I found it very interesting to follow Gamache as he struggles with not at all a clear-cut decision about what is the right thing to do. As I get older, it’s less and less black and white about what is right.”

This Saturday Vroman’s Bookstore will host a book signing and discussion at Colburn School’s Zipper Hall with Penny, whose numerous honors include six Agatha Awards and the Order of Canada. “Glass Houses” offers chewy meat for discussion. It’s haunted by a macabre creature, silent and ominously watchful, inspired by one she first learned of 20 years ago from a visiting friend from Spain: the cobrador del frac, who follows people and shames them into paying their debts. Without revealing too much, suffice to say that the cobrador incites suspicion, terror, bravery, and hard soul-searching.

“I thought, ‘One day I’m going to use this cobrador and the idea of conscience,’” Penny recalls. “It took 13 years or more until I felt that the characters were at such a stage, that I was at such a stage as a person and a writer, that the world was at such a stage to really do justice to the issue of the role that conscience plays in our lives.”

Part of what gives “Glass Houses” depth is the contrast between individuals believably struggling with issues of principle against a backdrop of cultures inhabited by amoral figures. The dignified Gamache (modeled after Penny’s late husband) is a man of integrity. Yet he methodically formulates a plan that violates every belief that grounds his life to achieve a lofty goal, sparking conflicts with suspects as well as neighbors and colleagues he respects.

“I found those impassioned arguments on both sides really interesting to write but also uncomfortable, thinking, ‘What would I do?’” Penny observes. “There’s a question we often ask ourselves: What would you do if you knew you wouldn’t get caught? Would you steal that? Would you have that affair? Would you kill that person? Oscar Wilde said that conscience and cowardice are ultimately the same thing, that the only thing that makes us do what’s right is the fear of getting caught. That’s a very cynical point of view, but it’s not necessarily inaccurate for some people. …

“I was reading a quote the other day: ‘Every journalist has a novel inside them, and that’s probably a good place for them.’ [Laughs] I always thought I would write a novel. From the age of 8 I wanted to be a writer. But I didn’t really know what I was going to write. There is nothing that separates good mystery novels or crime novels or murder mysteries from literary fiction, from science fiction, from romance. ‘Hamlet’ is a murder mystery. Good writing is good writing. The rest is packaging.” 

Vroman’s presents an evening with “Glass Houses” author Louise Penny at Colburn School’s Zipper Hall, 200 S. Grand Ave., Downtown LA, at 6 p.m. Saturday, Sept. 2; $37/$45. Info: (626) 449-5320. louisepenny.com, vromansbookstore.com