This is the magical legend of King Arthur retold through the eyes of the women behind the throne. Morgaine, (or Morgan Le Fay), and Gwenhwyfar, ( Guinevere), struggle for power, each promoting their respective beliefs and using Arthur. The time frame for the story is when Christianity was taking over the island of Britain. One of the things I find very interesting is how the traditional Arthur legend is changed when seen through the eyes of the women. This book is filled with strong female characters. It has intrigue, Camelot politics, romance, betrayal, magic, and explores Christianity v. Pagan and God v. Goddess. It is a very long and at times difficult book to read. Be prepared for that. I have read it more than once. I think it is a book you either love or hate, with no in between.
The second book in the series, The Forest House, is actually a prequel to Mists of Avalon. While not as good as Mists of Avalon, ( which I think is one of those books you can't top), I still enjoyed it. Eilan, the daughter of a Druidic warrior who is gifted with the "sight". She meets and falls in love with Gauis, a half Roman-half British youth, and son of the Roman Prefect Macellius Severus, second-in-command in Britainnia. They want to marry but neither family approves. So they are forced apart with Eilan living in the Forest House, dedicated to the Goddess. For the rest of their lives the two meet again and again. It has all the thrills, romance, heartbreak and magic that you expect.
Lady of Avalon, the third book in the series, is also told ahead of the time of Mists of Avalon. I think of it as a sequel to House and a prequel to Mists. The timing of this one is close enough to Arthur's Camelot that Merlin and Vivianne make an appearance. It is a bit different in that it is actually three books in one, interwoven in the Pagan belief of the life cycle. The first story, "The Wisewoman", picks up where House left off with Caillean and includes the life of Eilan's son Gawen. The second story is mainly about Dierna, who we meet in the fourth book, (which makes placing the fourth book in the series tricky). The third part, "Daughter of Avalon" is the story of Vivianne. It leads up to Mists of Avalon. I think it is a very important part of Mists as it gives a lot of insight to Vivianne and why she does the things she does in Mists.
The final book is Priestess of Avalon. I would read it after the first story in book three but before reading the second story. This book is set a lot outside of Avalon. It is the continuing story of Eilan, ( or Helene as she is now called). It also brings in Dierna, the High Priestess.
I love the the magic of these books. They are considered YA books although I read them as an adult and enjoyed them. There are two other books that are widely accepted as being a part of the beginning of the series. I have not read them. They are The Fall of Atlantis and Ancestors of Avalon, (written by Diana L. Paxson and I believe this is considered Book 5). The Fall of Atlantis is accepted as the beginning of the series. Ancestors of Avalon is the continuation with the move from Atlantis to Britain.
Ravens of Avalon and Sword of Avalon by Diana L. Paxson, are a continuation of the Avalon books. I have not read either of them. These books were written after the death of Ms. Bradley. Ms. Paxson co-authored The Forest House, Lady of Avalon and Priestess of Avalon.
All books are available from major bookstores, Amazon, Barnes & Noble. They can be found in used book shops, (where I got a few of mine). Some may be available for swap on Good Reads. Most of the books are available on Kindle.