I have enjoyed reading Robin Maxwell's historical novels, even though I don't always agree with her characterisations of certain persons, or her choices in terms of their actions. The Queen's Bastard is another such book - well-researched and written, fun to read, but not featuring "my" Queen Elizabeth.
Maxwell's premise is that Elizabeth not only consummated her relationship with Robert Dudley, but that early in her reign, she conceived and secretly bore him a son. As difficult as such a thing would have been to hide in the Tudor Court, Maxwell does manage to effectively present a just-barely-possible scenario. The complete disappearance of the child from history is explained by a secret plot-within-a-plot by Kat Ashley and William Cecil to replace the live baby with a dead one, convincing both Elizabeth and Dudley that their son did not survive birth.
The novel is structured such that we alternate between reading sections of a kind of autobiography written by the adult child of Elizabeth - interesting for their look at the life of a child raised as the younger son of a minor country gentleman who follows the path of many younger sons and runs away to become a soldier - and sections from Elizabeth's perspective detailing key points in her reign, with particular focus on the public events that shaped what is known about her relationship with Dudley.
It must be noted that Maxwell has based her novel on a real incident. Not long before the launch of the Spanish Armada, an Englishman giving his name as Arthur Dudley was arrested and interrogated by the Spanish before being placed in prison and disappearing from historical record. He claimed to be the bastard son of Elizabeth and Robert Dudley, and the story he gave to his interrogators formed the basis of Maxwell's story. Most historians have dismissed Arthur Dudley as either a pretender or an English spy telling a wild tale in an attempt to save his life.
Certainly, when cast as fiction, it is intriguing but not quite credible, to my mind. But once one suspends one's disbelief, it makes - in Maxwell's hands at least - a fine and enjoyable novel.