The Light Beyond the Forest provides an excellent introduction to the Arthurian legends, particularly the stories that relate to the quest for the Holy Grail.
The Holy Grail was believed to be the sacred cup used by Christ and his disciples at the Last Supper and then used by Joseph of Arimathea to catch drops of Christ's blood at the crucifixion.
Joseph was thought to have left the Holy Land to settle in England, bringing the sacred relic with him. Sutcliff bases her narrative primarily on Thomas Malory's Morte Darthur (1485), which is itself drawn from a thirteenth-century text by a Cistercian monk. Sutcliff strips away the repetitiousness of these medieval romances and focuses on the essentials of the quest, carefully balancing the tales of the four major characters who seek the Grail—Sir Lancelot, Sir Galahad, Sir Percival, and Sir Bors.