What are the morals of the book?
Although Twain's famous disclaimer to the novel was utterly scathing towards anyone who looked for a moral in the story, the book certainly does have moral concerns. Most centrally, these involve the development of the young narrator, Huck. He has to fight against the false morals implanted in him by society, which hold that it's wrong to help a slave to escape, as he tries to help Jim. But his own inner morality eventually triumphs, as he decides to lets Jim go instead of telling his owner, Miss Watson, where he is.
Society as a whole does not appear in a very positive light in this novel; there are many instances of injustice, violence, and hypocrisy. In fact, although it does not state it directly, the book seems concerned to show that individual morality is generally a better thing than the values much trumpeted by society.