“Katherine Swynford” by Alison Weir is a more scholarly treatise on the same subject, also worth the read IMHO. (My interest stems in part from my relationship to the deRoet family and part from my love of the study of history...that and $2.00 will get me a cuppa tea anywhere)
Cool! I'm related to Black Jack Pershing.
I read all the historical novels about the queens by Victoria Holt and the Anya Seton ones, when I was a girl, but I haven't picked up many of the more recent biographies.
However, a recent book about Anne Boleyn gave the impression that there's little more fact to the "nonfiction" books than the fiction, because the sources are so limited.