Short answers, pulled from the story.
Mark Twain was the pen name of Samuel Langhorne Clemens, an American writer, humorist, and essayist who lived from the 30th of November 1835 to the 21st of April 1910. William Faulkner called him the father of American literature.
The pen name Mark Twain comes from a leadsman's cry on the Mississippi River meaning a measured depth of two fathoms, or twelve feet, which was safe water for a steamboat. Twain first signed it on the 3rd of February 1863 while working at the Virginia City Territorial Enterprise.
Mark Twain wrote The Adventures of Tom Sawyer in 1876 and Adventures of Huckleberry Finn in 1884, the latter often called the Great American Novel. He also wrote A Connecticut Yankee in King Arthur's Court in 1889, The Prince and the Pauper in 1881, Pudd'nhead Wilson in 1894, Life on the Mississippi in 1883, and The Innocents Abroad in 1869.
Mark Twain lost most of his fortune investing in the Paige typesetting machine, spending three hundred thousand dollars on it between 1880 and 1894 before the Linotype made it obsolete. His publishing house also failed, and he filed for bankruptcy protection in April 1894.
Mark Twain turned against imperialism in 1899 after reading the treaty of Paris and concluding that the United States meant to subjugate rather than free the Philippines. From 1901 until his death in 1910 he served as vice-president of the American Anti-Imperialist League.
Mark Twain died of a heart attack on the 21st of April 1910 at Stormfield, his home in Redding, Connecticut, one day after Halley's Comet passed closest to the Sun. He was born shortly after the comet appeared in 1835 and predicted in 1909 that he would go out with it.