**Edited** I've just come back from reading reviews of another of her books called Wheel of Fortune. It appears she uses this retelling of English history through other's lives in her other books as well. I'm quoting below from a couple of Amazon reviews.
Cashelmara is based on the story of Edward I, Edward II, and Edward III, ending as Edward III overthrows his mother's lover and claims the throne as his own. The Wheel of Fortune picks up the same story about half way through Edward III's life (he is now Bobby Godwin), and follows the story through the life of his sons Edward The Black Prince (Robert), John (John of Gaunt) and Thomas (Thomas of Woodstock), his grandsons Kester (Richard II) and Harry (Henry IV), and his great grandson Henry V (Hal).
Will definitely have to get that one, just to see how she does with John of Gaunt and Katherine Swynford!On the last inside page, S. H. says in Author's notes "The Wheel of Fortune is a re-creation in a modern dimension in which the following people play leading parts:
Edward of Woodstock, 1330-1376, The Black Prince
His wife and cousin, Joan of Kent
John of Gaunt, his brother
His younger son, later King Richard 11
John of Gaunt's legitimate son Henry of Bolingbroke, later King Henry 1V who restored England to her former military glory and completed the full circle of the Plantagenet family's wheel of fortune.