In fiction, the less descriptive details detract from creating suspension of disbelief, the less they might drag a reader out of the story to say, “Nuh-uh! No way! Not so!” and so getting the little things right can make a difference in verisimilitude and suspension of disbelief, let alone simple enjoyment of a story well told.
Let me offer a very small example (one of, sadly, more than a few from a book now in hand):
Speaking about an event in Atilla’s life tied to a specific town in Italy in 452 A.D., a learned gentleman intones,
“The town was founded in the first century, so it was already three hundred years old when Atilla arrived.”
Really? Any (and I do mean ANY) literate person knows that the first century A.D. began with year 1 and went through 100 A.D. 452 A.D. was squarely in the middle of the FIFTH century. It would have made sense to have said, “The town was founded in the first century, so it was already FOUR hundred years old when Atilla arrived.”
When a novel that relies heavily on historical citations (and legends tied to history) begins to pile up errors like that, it starts to seriously detract from the story.
No, before you ask, it’s not a book by Dan Brown. It’s not within several orders of magnitude of being THAT bad. In fact, apart from niggling little things like the one noted above, and quite contra a Dan Brown prose atrocity, it’s actually pretty good reading, which is what makes these niggling little problems… problems.
Hey, it beats 2 seconds per channel with the TV clicker sayin’ “Bored now. Bored now. Bored now. Bored now… ” *heh*