For the King’s Favor is about Ida de Tosney, a mistress of Henry II, and the mother of one of his illegitimate sons, and her eventual husband, Roger Bigod. Chadwick apparently stumbled across Mahelt, the because the oldest daughter of William Marshall (who Chadwick seems to have a bit of an understandable crush on) and Isabelle de Clare, who her last two books were about. (Mahelt’s book To Defy A King just came out in the US.)
There’s a lot less historical record regarding Ida and Roger than there is regarding Isabelle and William, and it shows at times, though that isn’t a bad thing. Interestingly, the William Marshall books were at their most interesting once William and Isabelle were married and surviving various political intrigues, even if the earlier parts may have technically been more exciting, while Ida and Roger’s story is more interesting when she’s still Henry’s mistress and he’s fighting for his inheritance, and less since they’re married. Roger’s part of the story focused a lot on inheritance laws and, well, I have a thing for historical inheritance laws, so that may be a YMMV thing. Ida’s situation is presented as kindly as can be without romanticizing it or glossing over the choices a young woman with little protection would have had if she caught the king’s attention. It was presented realistically, but not to such a degree that a modern reader would be actively uncomfortable reading it.
Chadwick’s books fall into that category of fiction that’s romantic historical fiction with a feminist slant, but unlike a lot of authors, she doesn’t infuse her characters with semi-modern sensibilities so much as she tries to take a realistic look at things with her own views shaping the narrative’s perception, which is a distinction I don’t think a lot of authors (authors I also like, I add) are quite able to pull off. Notably, what we know of Ida in history makes her less easily approachable to modern readers than what we know of Isabelle, and I appreciate that Chadwick didn’t try to mold her into someone a lot of readers might find easier to identify with, and instead focused on what she would have had to face and how a woman of the time would have dealt with it. (Which is to say…uhm I actually do like Isabelle more, both in fiction and in history, but I don’t like or appreciate Ida any less for it.) Another thing about Chadwick is that, unlike a lot of authors of historical fiction, she doesn’t jump at the chance to pit the women of history against each other, even when it would be easier than portraying a more positive relationship between them
I really wish most of her books weren’t currently out of print in the US.