The Unknown Shore is the second (and arguably the weaker) of the two seafaring novels that Patrick O'Brian wrote before embarking on the epic Aubrey-Maturin series that would occupy him for the rest of his life. Like the Golden Ocean, it's set during Commodore Anson's circumnavigation of the globe in 1740, but this time focuses on the misadventures of the crew of the store ship Wager after it is wrecked off the coast of Chile. The two central protagonists are Jack Byron, a resourceful midshipman, and an eccentric surgeon's mate called Tobias, and much of the second part of the book (following the shipwreck) revolves around their battles to survive among indifferent or hostile natives, and their increasingly desperate attempts to return to civilisation.
Like all Patrick O'Brian's naval fiction, the novel is characterised by glittering wit and prose, convincingly archaic dialogue, and research so exhaustive and immersive that it convinces you it was all somehow collected at first hand. However it lacks some of the deftness and lightness of the Aubrey-Maturin novels. Occasional passages feel overwritten, the humour is sometimes laboured, and certain characters are unconvincing - none of which is really fair criticism, since I'm comparing them to later O'Brian, and he had more than four decades to perfect his art. Also the fact that Jack and Tobias are so obviously prototypes for Aubrey and Maturin can actually be pretty distracting in retrospect, especially as there are a handful of slight but significant differences in their characters which can seem strangely jarring if you're familiar with the later novels.
I don't think this novel represents Patrick O'Brian's best work, but it's still an entertaining and gripping read, and it's still head and shoulders above any other authors in the genre.