It may sound as though I'm damning with faint praise, as I probably sound less than enthusiastic. And that would be true. Historically the novel is accurate, at least on the bigger picture. However there are lots of flaws. Where Charles has a precise quote from one of the principal characters, he quotes direct in Tudor English, so there's a very strange juxtaposition of 21st century slang with Shakespearean English. As a result the novel never feels entirely comfortable in its own skin, or rather the century to which it is meant to belong.
The novel centres around a young man, Richard Stocker, the son of a Devonshire farming family, who becomes caught up in the Grey household, and gets to know them intimately. Stocker's voice is a useful one, an outsider who becomes a sort of insider, well able to follow the family through a most extraordinary period. However here too there are problems. I find it hard to believe that someone of farming stock would rise so high in the favour of this noble family - even having an affair with one of the daughters. I'm not saying it didn't happen (Thomas Cromwell after all was the son of a blacksmith, although he also had merchant connections), just that it seems rather unlikely.
The other thing is the "Yeuch!" factor, which in this novel is pretty big. In order to become party to the family secrets, Richard falls in love with the middle Grey daughter, Catherine (who would later become an ancestor of the Queen Mother!), who would have been 11 years old at the time. Even allowing for the different values of the time, all the Grey children appear to be extraordinarily mature in their outlook, while the Grey parents come across as immature, and incapable of dealing with life at court. Jane's father is alternately presented as adroit and manipulative, or extraordinarily stupid; and as a result comes across as a cardboard caricature of a man.
The author is clearly very keen on his subject, but the writing is clumsy. In the shadow of Lady Jane is great if you want a readable overview, just remember to read it with a copious pinch of salt.