This book is riddled with narrative flaws and delivery problems. In short, it feels like the author had 2 different ideas for a book, mashed them into one because he didn't have enough ideas to flesh either out to a full-length book, and published the first draft.
The saddest thing about the narrative is that a story about a band of smugglers and a story about the Jacobite cause could potentially work well together. However, because of the way Preston decides to structure his story, it does not work at all. A story usually has an exposition, a rising action, a climax, and a denouement - in the case of Winchelsea, there is an exposition followed by about 200 pages of narrative that is too monotonous to be considered rising action, or any kind of development. The only real climax to speak of takes place in the last 30 pages of the novel, which is quite well written. This means that, for example, the journey of Goody throughout the novel feels sporadic and unexplainable from her point of view, especially in the latter half of the novel.
However, easily the biggest weakness of the novel is the delivery. Preston clearly has a wide vocabulary, and he is not afraid to use it. This would not be a problem, except for the fact that it is used ineffectively. Regardless of their upbringing, origin, age, environment, class, occupation, or current situation, every single major speaking character and narrator speaks with exactly the same cadence as any other, needlessly abusing unusual grammatical structures, antiquated vocabulary (with noticeable spelling errors too), and run-on-sentences, all without any sense of taste or purpose. This becomes a massive problem throughout the book; oftentimes it becomes increasingly difficult to tell who is speaking, because everyone sounds exactly the same. This becomes doubly frustrating when the narrator changes about three quarters of the way into the novel, and again 40 pages before the end of the novel. I did not have any issue with this on its own as much as other readers; the change is quite reasonable considering the context - it just does not work because neither of the narrators sound distinct from Goody in the slightest.
Additionally, it is almost impossible to feel at all attached to any of the characters in the novel, bar one - the only real observable character development is with Arnold Nesbitt, a character who shows up at the start for a few pages, gets hit on the head by Goody, disappears for the majority of the story, and then narrates the last 40 pages of the story. Unfortunately, he is the only character in the story who seems to not be one-dimensional. Otherwise, Goody, the main character of the novel, is a completely static character that for the most part lacks agency or purpose, and the few instances that she makes decisions of her own (e.g. deciding to live as a man or fighting for the Jacobite cause after the death of her brother) are few and far between, and usually come out of nowhere only to be justified many pages later.
All of this to say, the book is not without redeeming qualities. The action scenes are well-written and full of tension, and they feel like oases of actually engaging writing amid the dreary and dull desert expanses of Goody's aimless and impersonal monologuing. The last 40-50 pages, as narrated by Arnold Nesbitt, are interesting as well.
I can definitely see Alex Preston's intentions with Winchelsea - it was meant to be a swashbuckling adventure spanning the entirety of Europe, as told from the perspective of a smuggler not quite comfortable in her own body. The skeleton of a good story is still present in this novel, but it is needlessly padded out by the blubber of an unengaging and underdeveloped narrative.
PS. The weird justification by the author at the beginning, where he justifies writing the story from a female character's perspective, is nothing short of unnecessary.