I have liked very much at different times "The Once and Future King" by T. H. White and "The Mists of Avalon" by Marion Zimmer Bradley.

Both are far inside me from having been read more than once in a way related to the hope of the heart.

Both are retellings of some of the King Arthur stories.

You can retell it anyway you want, but the King Arthur series is sad.

Two big ways it is sad are

1. A man has an affair with his best friend's wife, a woman has an affair with her husband's best friend--same thing from different angles.

2. A serious and real attempt to live better falls apart.