Since the plot hinges on the toss of a coin, the entire novel is a matter of opposites: Jacobite and loyalist, older and younger brother, wanderer and steward, lover and husband, charm and restraint, selfishness and duty. And at the centre of it is a struggle over who merits their place as the hero of the novel: the feckless, charming, amoral and ambitious Master, or his stolid, honourable, introverted and subtly dull younger brother, who through the toss of a coin suffers one side of an extraordinary inversion, becomes the laird, husband and father, while the bold, talented heir becomes a wondering adventurer. Stevenson seems almost as fascinated by testing, or reframing, the very nature of a hero in an adventure plot.
But, the economy of detail, the absolute precision of characterisation through action, is almost perfect. Perhaps only a novel based on chance can be this finely, exactly, constructed and controlled.