The novels are connected via Avalon itself and the implication (strongly hinted at, though rarely outright stated) that several characters throughout the series are the same souls reincarnated.
First established in The Mists of Avalon, the series' version of the legendary island is notably different from other depictions, though it draws from and expands earlier legends.
The author was influenced by traditions of neo-paganism (which Bradley herself once practiced) that conflate or associate similar pagan deities and emphasize a matriarchal religious structure.
Morgaine's desire to preserve the matriarchal pagan religion of her people leads her to develop an enmity for Christianity, a newly rising power in Britain, and to come into conflict with her brother.
Set in the first century CE during Roman occupation of Britain, The Forest House (1993) focuses on the pagan religious order which predated the founding of Avalon.
Among these are the stories of Caillean, the High Priestess who casts the spell that conceals Avalon in mist, Dierna, who arranges a marriage between a British princess and a Roman officer in an effort to secure peace, and Viviane, a character from the original novel.
In the story chronology the earliest book of the series, Ancestors of Avalon (2004) tells of a group of refugees from the lost continent of Atlantis who settle in Britain.
Taking place prior to The Forest House, Ravens of Avalon (2007) adapts the story of the historical Celtic warrior-queen Boudica of the Iceni tribe, who resists the rule of Britain by the forces of Rome.
Vowing vengeance for the invaders' violent rape of her daughters, Boudica raises an army and calls upon the Goddess in her fearsome warrior aspect.
Mikantor, the "Son of a Hundred Kings" and rightful ruler of the British tribes, is sold into slavery while the cruel warlord Galid usurps control of the land.