I'm receiving email regarding details in Fidèle, which fills me with bliss because it means that people are recognizing the extent to which I've obsessed over those details.
That my other published stories were Tolkien fanfic should explain this obsession. I'm vague when I have to be (the identity of "the city" even though it's fairly obviously New York City, which will be made clear in a dozen chapters or so, the village in Wales that appears in the prologue and that I'll never identify because it's too small to get the geography wrong) and very, very specific when I want to be. I did indeed engage in world-building for this story. I know things about the characters that will never appear in the main narrative. I have a day-by-day record of everything that happened and where everyone was at the time.
But I do most definitely encourage scrutiny. If a detail seems off, let me know.