Long John Silver is the book's most powerful and developed character, one whose motivation is believable but not unambiguous and whose complexity makes Treasure Island a true work of genius. Silver is much more than a type; he is a genuine individual, attractive and repellent by turns, frightening at times and at other times nearly sympathetic, always compelling.
Unlike the other characters, Silver is presented in specifics: You know his age, his appearance, and something of his history. He is the only one who seems to have a life outside the novel, a past and a future for which there is actual evidence in the text. And he is the only character who is presented against type; Jim describes him as "intelligent and smiling . . . clean and pleasant-tempered" — very different from what he expects a pirate to be. Silver further convinces Jim (and perhaps the reader, too) that he is not Billy Bones' "seafaring man with one leg" by sending runners out of his tavern after Black Dog and going back with Jim to report on the incident. He is frugal, plans ahead, speaks respectfully to Trelawney and the others, and is known for being sober and abstemious in his habits. In other words, although you may see Long John Silver now as the archetypal pirate, complete with peg leg and parrot (and maybe an eye-patch thrown in), he was certainly not that to Stevenson's first readers.
Silver is portrayed in the round, from various angles. His honesty and forthrightness are convincing to Livesey and Jim at first because he truly is honest and forthright, hiding his true motive but not his true personality. He controls the other mutineers as well as anyone can by force of his personality, his strength of mind, his courage, and his real cheerfulness. He has supreme control of himself, physically and mentally. Even his brutality is controlled; when he takes the reluctant crewman Tom apart from the others it is clear that he wants to persuade the man, not to kill him; but, when they hear the others kill Alan, Silver knows he must be rid of Tom, too, and he accomplishes this so swiftly and coldly that the reader's shock is nearly as great as Jim's.
Is Silver fond of Jim, does he feel affection for the boy who could be the age of his son (if he has a son; Black Dog has said he does, and that boys need discipline)? If Silver did not like Jim he would ignore him, for his first motive in arranging this voyage and mutiny is cash ("all that blunt"), and Jim can be of no use to him in that regard. The turning point in the relationship between Jim and Silver — at least as far as Silver is concerned — is Jim's bravado admission to having hidden the ship and killed Hands. Silver does not doubt him; one may guess that he sees something of his own courage and sense of purpose in the boy. And now he stands by Jim at the risk of his own life, when he could easily give him up to the others or kill Jim himself (as he has killed Tom, a much longer acquaintance, apparently without a qualm). He tells his men that Jim is a hostage and tells Jim that he is a potential witness in his favor, but Jim is a liability to him really. Still, he says, "Ah, you that's young. You and me might have done a power of good together." One cannot doubt the affection and regret in this statement. But a half-day later, under the spell of the treasure, he is ready to kill Jim and get on with it.
Which is the real Silver? Probably, they both are. Another Stevenson novel speculates famously that there are at least two sides to every person and most likely a lot more than two. Real people are self-contradictory, although the basis of the contradiction may be a deeper consistency. Silver intends to live comfortably and well; he hates Trelawney, and one may guess this is because Trelawney, foolish as he is, was born to wealth and Silver was not. He wants the freedom and luxury to live his old age openly and happily, and the peculiar set of experiences that his life so far has brought him allows him to commit the darkest crimes to gain these things.
Note that in the 1934 film, it is Jim, not Ben Gunn, who helps Silver to escape, but Stevenson's Jim cannot be so self-contradictory; his morality, like the others', is conventional, black and white. Silver is amoral, or perhaps he is true to his own strange morality. Ultimately, it is Stevenson himself who allows Silver to escape, sending the others ashore and giving him leave. Like Jim, the reader is glad to see him go.