A Connecticut Yankee in King Arthur’s Court was published in 1889. At the time Twain wrote the novel, half of Europe was still dominated by monarchies and empires, who often greatly restricted teh freedoms of their subjects.
This novel has several aspects. Twain made a roaring good adventure tale, yet it the book is also a bit of social commentary on 19th century American and 19th century Europe. The main character expresses his opinion of the organized religion of the Middle Ages. There is also several scenes where Twain is using the story to express perspectives on social class systems, where one class is greatly oppressed such as Medieval peasants.
Many of the traditional tropes of an Arthurian medieval romance are there, but with a bit of historical accuracy of the medieval society included. The main character brings in many of the positive aspects of the American national character of the late 19th century.
In the context of the Arthurian Cycle, the book does not add that much. It is a story that uses the appeal of King Arthur for a ready audience more than trying to explore Arthurian Lore. This is not a bad thing; if anything it allows a reader to enjoy the story and have a ready set of tropes to build expectations.
The most enjoyable part of the the story is the contrasting of Twain’s interpretation of a modern world view as opposed to a medieval world view.