The Once and Future King by T. H. White

Once upon a time, a young boy called “Wart” was tutored by a magician named Merlyn in preparation for a future he couldn’t possibly imagine. A future in which he would ally himself with the greatest knights, love a legendary queen and unite a country dedicated to chivalrous values. A future that would see him crowned and known for all time as Arthur, King of the Britons.
 
During Arthur’s reign, the kingdom of Camelot was founded to cast enlightenment on the Dark Ages, while the knights of the Round Table embarked on many a noble quest. But Merlyn foresaw the treachery that awaited his liege: the forbidden love between Queen Guenever and Lancelot, the wicked plots of Arthur’s half-sister Morgause and the hatred she fostered in Mordred that would bring an end to the king’s dreams for Britain—and to the king himself.