Growing up, Mark Twain was friends with a poor and abused boy named Tom Blankenship. These characteristics are reminiscent of those of Finn's, but the real proof lies in Twain's autobiography, where he writes: "In Huckleberry Finn, I have drawn Tom Blankenship exactly as he was. He was ignorant, unwashed, insufficiently fed; but he had as good a heart as ever any boy had." Do take this notion with a grain of salt, though. During an interview in 1885, Twain was asked on whom Huckleberry Finn was based. He said he couldn't point to a specific person, but said: "still his story is what I call a true story."
The plot of the book takes place before the Civil War. Huckleberry grew up in the south. At the beginning of the book, not only does he accept slavery but he also believes that helping Jim escape is a sin. By the end of the book, his beliefs are turned around completely. Growing up in the south himself, Twain also grew up around slavery. His uncle owned 20 slaves. When he grew up, his views changed. He married into an abolitionist family, and his father-in-law even helped a slave escape slavery.
The main reason this book is considered by many to be the first-ever truly American novel is that it was the first to be written in American vernacular. The plot of the book is told in the first person by Huckleberry Finn himself. He speaks in dialect, using grammatical errors that were widely used in his time and region. This was considered revolutionary. It makes the reading experience more vivid and still influences how Americans write today.
The first time the book was banned was a year after its publication in 1885. The reason was the writing style - it was rendered trashy and cheap instead of natural and realistic. The most common reason to ban the book was various forms of racism: there's wide use of the N-word and there are claims regarding the racist portrayal of African-Americans. Two different versions of the book have been published - one replacing the slur with the word "slave," and one replacing it with the word "hipster."