This is an 1889 novel by one of the greatest writers in the history of American literature, Mr. Mark Twain. It was published more than a century ago, but it's still an awesome read today, in 2016, simply because Twain's amazing writing style, rich, likable characters, and exciting narrative make it "fit" for all times, ages and nationalities.
A Connecticut Yankee in King Arthur's Court features an engineer from the US who travels through time and ends up in King Arthur's court. In order to survive in this new, harsh reality, he convinces the people of the kingdom that he's a first-grade magician and uses his knowledge of technological developments from his time to further prove his worth. He amazes the Middle-Age English folks with bombs, fireworks, and more advanced tech.
The Yankee tries really hard to modernize King Arthur's army, but he still fails to prevent his death. Furthermore, the Catholic Church marches against him, simply because it feels threatened by his powers. They say Mr. Twain wrote this story after he had a dream with a similar plot. Regardless, A Connecticut Yankee in King Arthur's Court is an amazing science fiction novel that comes with a wonderful sense of humor, jokes about the English chivalry, an interesting concept and, of course, Twain's trademark brilliance.
And one of the greatest things about this book is that it's equally great both for the grown-ups and for the kids/teenagers, as readers of all ages will find something truly awesome in it. The incredible mix of comedy, satire, fantasy and science fiction makes it a highly entertaining, educational and all-around satisfying read.