The narrator in the novel is Huck Finn himself. He tells the story from his point of view as a young man and in his own dialect and language. The eNotes study guide tells us that this novel is "one of the first in America to employ the child's perspective and employ the vernacular—a language specific to a region or group of people—throughout the book."
Not only do we hear Huck's own voice in the novel, but through his relating of his adventures, we hear other southern dialects, such as that of former slaves. All of this comes from the perspective of a child in the post-Civil War era.
The narrator of this novel is Huck Finn himself. He is a young boy without a mother and whose father is considered the town drunk (when he's around at all). We learn a lot about Huck Finn in just the first few paragraphs of the novel. He tells us who he is, but also mentions the book is being written by Mr. Mark Twain, who also wrote Tom Sawyer - so, from the beginning, we are directly told that the events will come from the pen of Twain through the mouth of Huck Finn. Being twice removed from the story gives it a hint of question-ability which is increased when Huck confesses that Twain did tell some 'stretchers' in the first book - leading us to believe he could tell some 'stretchers' in this one as well. Huck goes on to give us other info, such as his negative views of religion, civilization, and eventually slavery. Because the novel comes from supposedly such a young perspective, the reader easily accepts Huck as innocent and honest making easier for Twain to express his message through his narrator.