I am at the half-way point of this long novel. The titular characters have only just met for the first time, aboard a passenger ship to Australia. Lucinda is returning home after a visit to England and Oscar is leaving England to serve as an Anglican minister in New South Wales. The back-story leading up to each of their embarkations aboard the Leviathan has been unfolded over more than 200 pages and numerous short chapters, but I would be hard put to say exactly when the actual main thread of the story appears.
The story is told by an omniscient narrator parading as a descendant of Oscar's. I haven't got far enough in the story to know if Oscar and Lucinda end up having descendants in common, but the narrator refers to Oscar as his ancestor but not Lucinda, so I doubt it. The story, up to the embarkation aboard the ship, is an unfolding of the influences that have made the titular characters as they are. Both are socially awkward and find it difficult to read people, but whereas Lucinda is fully aware of her awkwardness and is often ashamed of not knowing how to behave and acutely conscious of people's opinion of her (actual or perceived), Oscar seems to think himself a perfectly ordinary fellow and simply doesn't understand that there could be anything the matter with his behaviour or appearance.
These formative experiences that are described in the first 200 or so pages of the book are important for an understanding of what has made Oscar Hopkins and Lucinda Leplastrier the way they are, and some of the events described therein may also reflect on later events. In any case, I wouldn't have left out a single word, because although I generally don't much like long back-stories, it really doesn't matter when they are as much fun to read as this one.
The titular characters both stand on the fringes of society , Lucinda because of the combination of her gender and her unconventional behaviour, and Oscar because he is just plain weird. While they have this fringe position in common, they are in other ways clear contrasts to each other, and not just because of the most obvious difference. She appears to be an atheist while he is quite religious, she is rich while he is poor, she always seems to be well-dressed while he dresses like a scarecrow. What brings them together is gambling. Both are addicted to games of chance, Oscar mostly to horse-racing and Lucinda to card-games, but both bet on other games of chance as well. Knowing a little bit about the story, I know that they will enter into a big wager, but not the outcome.
I am now at a point in the story where Oscar has, quite innocently and unwittingly, ruined Lucinda's reputation (according to the ship's crew, anyway), by staying in her room to play cards.