Before the main novel begins, there are two sections (the Preface and 'A Word of Explanation') that must not be overlooked.
In the short Preface, Mark Twain uses irony to introduce how this novel draws on history, but does not pretend that the 'ungentle laws and customs' are specific to the 6th century. He also claims that the subject of the divine right of kings is not settled in this work as the debate 'was found too difficult'.
In 'A Word of Explanation', a first-person narrator (who the readers are led to believe is Mark Twain) is visiting Warwick Castle and begins a conversation with a 'curious stranger'. This stranger talks of the Knights of the Round Table as though they are friends. The stranger then talks of the transmigration of souls and claims that he is to blame for the bullet hole in the chain mail of Sir Sagramor Le Desirous, who was alive in the 6th century. It is not until Chapter XXXIX that the readers are told of how this happened.
That night, after the narrator has read an excerpt from Sir Thomas Malory's Le Morte D'Arthur concerning Sir Kay and Sir Launcelot, the stranger comes to his room in the Warwick Arms and begins to explain his story a little more. This comes under the subtitle 'The Stranger's History'. Here, the stranger takes over the narrative with the use of the first person as the readers learn of the past of the eponymous Connecticut Yankee (whose name is Hank Morgan).
Hank tells of how he was born in Hartford, Connecticut and learned to be a blacksmith and a horse-doctor. He then went to work in an arms factory and became the superintendent of a couple of thousand men. He describes how after a fight, he woke up in Camelot (in 6th century England) and was taken captive by a knight. The narrative returns to the present as Hank gives the first narrator his written account of his adventures in Camelot. This manuscript constitutes the main novel, which is composed of 44 chapters.
These initial passages, which include the Preface and the stranger's history, are vital to an understanding of the main novel as they set the scene and are useful indicators of Twain's use of irony and layered narration.
These early sections work doubly in both serving as a means to authenticate Hank's time-travelling experience, and also to underline that this is a fantasy. The fantastical aspect is emphasized with the points that the first narrator had been reading of Sir Kay's adventures before the stranger, Hank, comes to his room, and this is the same knight that captures Hank in Camelot in Chapter I. Further to these points, also bear in mind that this is a framed narrative because the novel begins and ends with M.T.'s narration.