Image: 

Adventures of Huckleberry Finn (1884 / 1885) (often shortened to Huck Finn) by Mark Twain is commonly accounted as one of the first Great American Novels.
The book has been popular with young readers since its publication, and taken as a sequel to the comparatively innocuous The Adventures of Tom Sawyer.

Plot summary:

Life in St. Petersburg

The story begins in fictional St. Petersburg, Missouri, on the Mississippi River. Two young boys, Tom Sawyer and Huckleberry Finn, have each come into a considerable sum of money as a result of their earlier adventures (The Adventures of Tom Sawyer). Huck has been placed under the guardianship of the Widow Douglas, who, together with her sister, Miss Watson, are attempting to "sivilize" him (sic). Huck appreciates their efforts, but finds civilized life confining. In the beginning of the story, Tom Sawyer appears briefly, helping Huck escape at night from the house, past Miss Watson's slave, Jim. They meet up with Tom Sawyer's self-proclaimed gang who plot to carry out adventurous crimes.

The Grangerfords and the Shepherdsons

While living quite comfortably in the wilderness along the Mississippi, Huck happily encounters Miss Watson's slave Jim on an island, and Huck learns that he has also run away. The two team up and shortly after missing their destination, Cairo, Illinois (in a free state to which Jim has planned to escape), Huck and Jim's raft is swamped by a passing steamship, separating the two. Huck is given shelter by the Grangerfords, a prosperous local family. He becomes friends with Buck Grangerford, a boy about his age, and learns that the Grangerfords are engaged in a 30-year blood feud against another family, the Shepherdsons.

The Duke and the King

Further down the river, Jim and Huck rescue two cunning grifters, who join Huck and Jim on the raft. The younger of the two swindlers, a man of about thirty, introduces himself as a son of an English duke and his father's rightful successor. The older one, about seventy, then trumps the duke's claim by alleging that he is actually the "Lost Dauphin", the son of Louis XVI and rightful King of France. The "Duke" and the "King" then force Jim and Huck to allow them to travel on the raft, committing a series of confidence schemes on the way south.
The Duke and the King's schemes reach their climax when the two grifters impersonate the brothers of Peter Wilks, a recently deceased man of property. Using an absurd English accent, the King manages to convince most of the townspeople that he and the Duke are Wilks's brothers recently arrived from England, and proceeds to liquidate Wilks's estate. Huck is upset at the men's plan to steal the inheritance from Wilks's daughters and actual brothers, as well as their actions in selling Wilks's slaves and separating their families.

Jim's escape

After the four fugitives flee farther south on their raft, the King "captures" Jim and sells his interest in any reward while Huck is away in a nearby town. Outraged by this betrayal, Huck rejects the advice of his "conscience," which continues to tell him that in helping Jim escape to freedom, he is stealing Miss Watson's property. Telling himself "All right, then, I'll go to hell!", Huck resolves to free Jim.
Rather than simply sneaking Jim out of the shed where he is being held, Tom develops an elaborate plan to free him, involving secret messages, hidden tunnels, a rope ladder sent in Jim's food, and other elements from popular novels, including a note to the Phelps warning them of an Indian tribe stealing their runaway slave. Huck and Jim go along with the plan, but Tom is shot in the leg during the resulting pursuit. Rather than complete his escape, Jim insists that Huck return to town and find a doctor to treat Tom. This is the first time that Jim demands something from a white person; Huck explains this by saying "I knowed he was white on the inside...so it was all right now." Jim and Tom are then captured and brought back by the doctor.

Conclusion

After Jim's recapture, events quickly resolve themselves. Tom's Aunt Polly arrives and reveals Huck's and Tom's true identities. Tom announces that Jim has been free for months: Miss Watson died two months earlier and freed Jim in her will, but Tom chose not to reveal Jim's freedom so he could come up with an elaborate plan to rescue Jim. Jim tells Huck that Huck's father has been dead for some time and that Huck may return safely to St. Petersburg. (Jim discovered this when he and Huck were on Jackson Island and came upon part of a house drifting down stream. The dead body in the house, which Jim did not let Huck see, was Huck's father.) In the final narrative, Huck announces that he is quite glad to be done writing his story, and despite Tom's family's plans to adopt and "sivilize" him (sic), Huck intends to flee west to Indian Territory.