For many generations now Howard Pyle's Arthur has been one of the standards for learning of the Knights of the Round Table. T.H. White is another. Both have brief tellings of each event, but Pyle's flows better, and White's also varies more from the accepted tradition. White uses more medieval sounding language, so some might prefer the romance of it.
Sequels are:
The Story of the Champions of the Round Table (1905)
The Story of Sir Launcelot and His Companions (1907)
The Story of the Grail and the Passing of King Arthur (1910)
related-King Arthur, Merlin, Queen Guinevere, knights & knighthood
RL=6th-YA