The Adventures of Huckleberry Finn is a sequel to The Adventures of Tom Sawyer and begins a few month after the end of Tom Sawyer. Both books are set in the southern United States. The plot is deceptively simple: a teenage boy runs away from home accompanied by an adult runaway slave. They journey down the Mississippi River on a raft and have lots of adventures.
During their journey, they encounter all sorts of people, some good and some bad. The encounters form the meat of the story. Among the most memorable of the bad characters are the King and the Duke, a pair of con artists who begin by persuading the then-naive Huck and Jim that they are royalty and deserve of special treatment. (This means, of course, that Huck and Jim do all the work on the raft.). But the King and the Duke are after bigger game: they hope to pass themselves off as the long-lost relatives of a recently deceased man, who was, of course, rich. By this time, Huck has realized the true and bad natures of these men--but he also realizes that if he goes along with the unsavory scheme that he and Jim could get part of the take....
Huck is faced with such decisions throughout the book. In a similar case, he learns that there is a substantial reward being offered for his friend Jim. If Huck turns him in, he could collect the reward money. He would also be obeying the laws of his society, which dictate that runaway slaves should be returned to their owners. Much as Huck likes Jim, he has felt some guilt over not returning him to his master. Huck must decide where his loyalties lie: with Jim, or with the society that made Jim a slave. He also must decide whether friendship is more important than money. The book is thus both an adventure story and a coming-of-age story in which Huckleberry sorts out his beliefs and loyalties.
Some people maintain that Huckleberry Finn is racist because of some of its language. I disagree with that belief for several reasons:
1) It was written in 1884, and the story is in the 1830s. Attitudes and terms that were acceptable then arent now. The word nigger, for instance, is now considered a highly offensive term for a black person. It was less offensive in Twains day.
Another thing to remember about the language is that the narrator is a poorly educated boy, so Twain deliberately uses bad spelling and grammar to convey Hucks lack of education. Twain also depicts different characters speaking different dialects, many of which would not be considered proper English. Luckily, Twain does not overdo this; the characters dialogue is still understandable.
2) The main black character, Jim, is Huckleberrys closest friend and is portrayed as a decent and kind person. Admittedly, he is also superstitious and ignorant, but thats because slaves received no education in those days, not because he is stupid. Besides, Huck himself is only marginally more educated.
Despite his flaws, Jim is certainly a more attractive and sympathetic character than the King and the Duke, or Hucks abusive and drunken father, or many of the other white characters in the book.
3) One of the subplots in the book is Jims quest for freedom. Jim joins Huckleberry on his journey on the Mississippi River because he is fleeing his master and hopes to go some place where he can be free. Twain treats Jim and his desire for freedom sympathetically throughout the book.
Some critics have complained that Jim is depicted as being too servile, but I suspect Twains point in such a depiction was to show the damage caused by slavery. Jim had spent his entire life as a slave, and had learned the servile habits that go with that status. During his time with Huck, he gradually learns how to conduct himself like a free person--which includes standing up to other people.