This author is reaching far beyond what other biographers and Tudor historians have been willing to assume. It declares that Henry was the father of Mary Boleyn's two children, Catherine and Henry Carey, who were both born after her marriage to William Carey and neither of whom were acknowledged publicly by Henry VIII. There is plentiful speculation as to whether they were or not, but no certainty, or even real evidence one way or another. This is extremely important, since she attributes some significant political motives to Henry VIII based on his supposed relationship to the unacknowledged Carey children that would have been out of character.
She also gives Chapuys, the Spanish ambassador, credibility without consideration of his acknowledged bias. Her discussion of the Duke of Richmond makes claims about Henry VIII's supposed directions to the Duke of Norfolk and his treatment of Richmond's widow, without ever quoting the correspondence that should contain these communications. In fact, Denny spends more space quoting other historians (often to show how they overlooked something she finds telling) than she does the subjects of the book. In the description of the fall of Anne Boleyn, she does not even mention Mark Smeaton, the lute player, or describe the motives of Jane Boleyn in ratting out her husband and sister-in-law.
This might be a fun read, but I wouldn't rely on it as an informative one. Alison Weir and Antonia Fraser have both written group biographies of the wives of Henry VIII that are much more informative, better cited, and more considered analyses than this one.