One of the things I enjoy so much about a Louise Penny book is the way she incorporates her research into her books. An example is Beautiful Mysteries, which is about silent monks who make Gregorian chants a central part of their faith and worship. I became aware of the depth of her immersion into the research when she noted that the monks’ silence awakened them to an awareness of minuscule expressions and the thoughts they conveyed. That is not something she learned from Wikipedia. (This is as opposed to The Tea Girl of Hummingbird Lane, about a girl from a hill tribe in China, Akha. When I looked up Akha, I found an entry that included all the beliefs and practices that were related in the book. I got no insights that would have come from someone having actual experienced living those beliefs and practices.)
Anyway, the thing that was so interesting in Glass Houses was the Cobrador. It is derived from the Spanish practice involving El Cobrador del Frac — a debt collector in a top hat who follows the debtor around silently, with the aim of shaming him/her into paying the debt. Penny created something different and more sinister by claiming it to be an ancient practice, and by making its purpose be to collect on moral and ethical debts as well as financial. I was disappointed to learn that she made that part up, and like the book a little less when I learned it was not true. I know; that’s not really fair.