The first chapter is loaded with regional idioms.
The book begins with this statement: "YOU don't know about me without you have read a book by the name of The Adventures of Tom Sawyer." The narrator is Huck himself, and the idiom is "without you," meaning "unless you."
Huck says that the book was by Mr. Mark Twain who told the story (of Tom Sawyer) "with some stretchers," meaning "lies."
He explains that at the end of the book, he and Tom had gotten rich from the treasure they found: "It was an awful sight of money when it was piled up," meaning it was a lot of money and looked really impressive when it was piled up.
Huck tries to take up the civilized life with the Widow Douglas, but "when I couldn't stand it no longer I lit out," meaning he left.
Tom brings him back home, but Huck is still restless: "After supper [the Widow Douglas] got out her book and learned me about Moses and the Bulrusher." "Learned me" is a regional idiom for "taught me."
Her sister, Miss Watson, comes to live with them "and took a set at me now with a spelling-book. She worked me middling hard for about an hour." That is, she was determined to teach him to spell, and worked him fairly hard at it for about an hour.