"Huckleberry Finn." Introduction Huckleberry Finn by Mark Twain. New York: Rinehart and Company, 1948.

Excerpt:

In 1876 Mark Twain published The Adventures of Tom Sawyer and in the same year began what he called “another boys’ book.” He set little store by the new venture and said that he had undertaken it “more to be at work than anything else.” His heart was not in it—“I like it only tolerably well as far as I have got,” he said, “and may possibly pigeonhole or burn the MS when it is done.” He pigeonholed it long before it was done and for as much as four years. In 1880 he took it out and carried it forward a little, only to abandon it again. He had a theory of unconscious composition and believed that a book must write itself; the book which he referred to as “Huck Finn’s Autobiography” refused to do the job of its own creation and he would not coerce it.

Online:
Google Books - published in The Moral Obligation to be Intelligent
Amazon - whole book