Hi Brian, I don't think in this case it matters - they could start here, if they wanted. I asked a test reader what they thought - (one who had not read the series, and I described what I thought it might affect) and their response was, when Verrain shows up, they will be a LOT more interested in that scene/having read The Gallant, first. And since that was a scene my editor wanted cut out of the book, this would, in fact, connect a dot that otherwise might not relate as well to a new reader into the series for the first time.
So I'd say, have at this one anywhere.
Nobody's reported back they finished it, yet…