That biography of Catherine ( the Frieda one) does try to portray her as a misunderstood person. She has been stereotyped for sure, by many sources. She was undoubtedly very political, very interested in politics. Yet for all that, her understanding of politics in France in that era wasn't the best. She seemed to think of politics in Medici terms, which worked in Florence, but not France. She wasn't a bad person, just in the wrong country, as the bad consequences of her meddling with politics shows. She should have stayed in Italy.
Mary Stuart was not at all political, but because of her position, she ended up dealing with politics. She didn't do a good job of it, although in Scotland as in France, these things were very complicated.Catherine and Mary were both raked over the coals because of politics often involving religion, although one chose that, and the other did not. Whatever the case, they both made messes of it. That's an interesting link between the two women. Another interesting link was that both were made to look bad later on in history, because of things that made them controversial. For Catherine, these were things like the Massacre of St Bartholomew, and her ambition for her sons, and France's religious problems. For Mary, there were things like the murder of Darnley, and her marriage to Bothwell, that led to to her leaving Scotland.