This is the book I most recommend for an introduction to traditional King Arthur (for older readers-Howard Pyle). The illustrations are dramatic and captivating. The language flows well, so it is good for reading aloud or for young readers.

related-King Arthur, Merlin, Arthurian romances, folklore of England, knights, knighthood, Lancelot, Guinevere, Holy Grail, sword in the stone, Tintagel
RL=3rd-6th