All of Mark Twain’s classic works had already been published by the time The Mysterious Stranger was posthumously published in 1916. In fact, The Mysterious Stranger is generally considered to be unfinished at the time of Twain’s death in 1910.
Twain is most famous for The Adventures of Huckleberry Finn (1884) and The Adventures of Tom Sawyer (1876). The Adventures of Huckleberry Finn is considered by many to be one the greatest American novels of all time. In fact, Ernest Hemingway said, “All modern American literature comes from one book by Mark Twain called 'Huckleberry Finn’.”
Twain also wrote a considerable number of short stories, essays, and nonfiction books (several devoted to travel).
The Mysterious Stranger is of considerable interest because there are several versions out there, and nobody can be really sure how Twain intended the novella to end.