Mark Twain's real name was Samuel Langhorne Clemens. He was born into a rich family in 1835, and he died 75 years later. His family owned many slaves.
He grew up on the Mississippi River, and went to work as a printer when he was 16. In his early 20s he started working on riverboats on the Mississippi. In 1861, when he was 26 years old, he joined the army from the South in the war between the States, but the men in his group ran away from the war because they did not believe in it.
He moved to Nevada with his brother, to look for silver, but two years later he started writing, at the age of 28. The Adventures of Tom Sawyer, printed in 1876, when he was 41, was, at the time, believed to be his best book.
He hired people to sell his books from door to door and made a lot of money; but he also wasted it. In 1884, when he was 49 years old, The Adventures of Huckleberry Finn was printed. It was much longer, and more serious than the earlier book. In this book Twain tries to get people to see the evils of slavery in an entertaining way.
Sadly, today there is much anger at his use of the word "nigger" in the book, because it has now become a very bad word. At a time when most great writers were using perfect English, Mark Twain chose to use the language of the people. This book is full of bad English, but it is the way that real people talked in real life in those days and in that part of the world.